- Networks
- Smart plugs and switches
Flashes once
Sonoff smart plug Flashes once: Wi-Fi or cloud offline
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
Flashes once (on BASICR4, or Quick flash on S60TPF and MINIR4) on the blue LED indicates that your SONOFF plug or switch is not connected to the Wi-Fi router. Check 2.4 GHz signal strength, router client capacity, and MAC filtering; if it flashes twice, eWeLink cloud is blocked.
Safety first
Stop and check this first
- Never bypass overload or overheat protection (Keep flashing), and never operate any connection or contact the terminal connector on wired SONOFF switches while powered on: always use a professional electrician with the upstream breaker turned off.
Safe checks you can perform
- Count the blue LED flashes per cycle to separate router, cloud, OTA, and overheat states
- Check 2.4 GHz SSID/password, router client capacity, range, and MAC blacklist (1 flash)
- Verify internet and regional coolkit.cc server access, then repower after 5 minutes (2 flashes)
Leave these tasks to a qualified professional
- Do not attempt this professional task: Diagnose 2.4 GHz Wi-Fi capacity, MAC filtering, and *.coolkit.cc cloud routing
- Do not attempt this professional task: Inspect load rating and terminal connections if Overheat protection trips (Keep flashing)
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Diagnose 2.4 GHz Wi-Fi capacity, MAC filtering, and *.coolkit.cc cloud routing
What they doThe technician checks 2.4 GHz signal strength at the installation point, verifies router client capacity and MAC filtering tables, and tests DNS/outbound reachability to the regional eWeLink dispatch server (*.coolkit.cc).
They must show youverified router association, unblocked *.coolkit.cc reachability, and the solid blue LED indicating Online status.
In writingresolved network condition (2.4 GHz signal, router client capacity, MAC filter, or coolkit.cc access) and online eWeLink status.
Inspect load rating and terminal connections if Overheat protection trips (Keep flashing)
What they doIf a wired SONOFF switch (such as BASICR4 or MINIR4) triggers Overheat protection or power dropouts, a professional electrician switches off the upstream 10 A MCB/RCBO breaker, inspects terminal wiring under the protective cover, and verifies the load does not exceed 10 A / 2400 W.
They must show youthe switched-off 10 A MCB/RCBO breaker, intact terminal connections under the protective cover, and verified load current.
In writingelectrical and thermal inspection report confirming load within 10 A / 2400 W and secure terminal connections.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Count the blue LED flashes per cycle to separate router, cloud, OTA, and overheat states
- Who:
- you, observing the blue Wi-Fi LED indicator on the SONOFF plug or switch.
- How:
- count the flashes between pauses: 1 flash (or Quick flash outside pairing mode) means router not connected; 2 flashes means connected to router (LAN) but not cloud; 3 flashes means OTA firmware upgrade in progress; continuous flashing on BASICR4 means Overheat protection.
- Result that matters:
- identify which exact operational or protection state the SONOFF indicator is signaling.
- If the LED flashes three times (Flashes three times):
- leave the device powered on until the OTA firmware upgrade finishes.
- If the LED flashes once or twice:
- proceed to the router or eWeLink server checks below.
- Evidence to keep:
- exact number of blue LED flashes per cycle and device status icon in the eWeLink app.
Evidence: S60TPF User Manual · BASICR4 User Manual · MINIR4 User Manual
Check 2.4 GHz SSID/password, router client capacity, range, and MAC blacklist (1 flash)
- Who:
- you, in your Wi-Fi router administration panel.
- How:
- make sure the SONOFF MAC address is not in your router's MAC management blacklist, disconnect unnecessary Wi-Fi devices if the router has exceeded its client capacity, shorten the distance or clear obstacles blocking the 2.4 GHz signal, and verify valid Wi-Fi credentials.
- Result that matters:
- restore 2.4 GHz router association so the blue LED stays solid on (Keeps on: Online).
- If removing a MAC block, freeing router capacity, or moving the router closer restores connection:
- the LED turns solid on.
- If your router Wi-Fi SSID or password was changed:
- press and hold the pairing button for 5 seconds to input the new credentials in eWeLink.
- Evidence to keep:
- screenshot of the router MAC management list and connected 2.4 GHz client count.
Evidence: Blink! Blink! SONOFF Product is Talking to You
Verify internet and regional coolkit.cc server access, then repower after 5 minutes (2 flashes)
- Who:
- you, checking router internet access and the eWeLink app on the same LAN.
- How:
- if the LED flashes twice, verify your Wi-Fi network can access the Internet and confirm with your ISP that the regional eWeLink server is not denied (eu-disp.coolkit.cc in EU, us-disp.coolkit.cc in US, as-disp.coolkit.cc in Asia, cn-disp.coolkit.cc in China Mainland); then pull down to refresh eWeLink, power off the device, and repower it in 5 minutes.
- Result that matters:
- reconnect the device to the eWeLink cloud server, or if continuous flashing indicates Overheat protection, unplug the load to let it cool.
- If refreshing the eWeLink app and repowering the unit after 5 minutes clears the two-flash state:
- cloud control is restored.
- If a wired BASICR4 keeps flashing continuously (Overheat protection) or feels hot:
- switch off the breaker and call a professional electrician.
- Evidence to keep:
- reachability of the regional *.coolkit.cc address and LED state after the 5-minute power cycle.
Evidence: Blink! Blink! SONOFF Product is Talking to You · BASICR4 User Manual
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Networks
- Brand
- Sonoff
- Product type
- Smart plugs and switches
Known code variants
- Flashes twice (LAN sin nube)
- Flashes twice (LAN without cloud)
- Keep flashing (Overheat protection)
- Quick flash (Router not connected)
What it means
In official SONOFF user manuals and the LED status guide, Flashes once (on BASICR4) or Quick flash (on S60TPF and MINIR4) means the device is not connected to the Wi-Fi router (No WiFi Connection), so it can only be switched manually via the physical button. When the blue LED Flashes twice (Flash twice), the device is connected to the router (allowing local LAN control on the same network) but fails to connect to the eWeLink cloud server (No Server Connection). In addition, on BASICR4 a continuous Keep flashing state indicates Overheat protection. An offline blink pattern alone never proves that the hardware is defective.
Warnings and stop conditions
- Highsource verified
Never bypass overload or overheat protection (Keep flashing), and never operate any connection or contact the terminal connector on wired SONOFF switches while powered on: always use a professional electrician with the upstream breaker turned off.
Evidence: S60TPF User Manual · BASICR4 User Manual · MINIR4 User Manual
Symptoms and causes
Probable causes · in order
- Wrong Wi-Fi credentials, exceeded router capacity, weak 2.4 GHz signal, or MAC blacklistCommon
SONOFF lists four official reasons for No WiFi Connection (1 flash / Quick flash): wrong SSID or password, exceeded router client carrying capacity, weak 2.4 GHz signal due to distance/obstacles, or MAC address blacklisting.
Evidence: Blink! Blink! SONOFF Product is Talking to You · S60TPF User Manual · BASICR4 User Manual
- Connected to router in LAN mode but blocked from eWeLink server (Flashes twice)Possible
When the blue LED flashes twice, the device is associated with the router but cannot reach the regional eWeLink server (eu-disp.coolkit.cc, us-disp.coolkit.cc, as-disp.coolkit.cc, or cn-disp.coolkit.cc).
Evidence: Blink! Blink! SONOFF Product is Talking to You · S60TPF User Manual · MINIR4 User Manual
- Overheat protection activated on the smart switch (Keep flashing on BASICR4)Less common
According to the BASICR4 user manual, when the blue Wi-Fi LED keeps flashing continuously (Keep flashing), the unit has entered Overheat protection.
Evidence: BASICR4 User Manual
Virtual technician
Does Flashes once still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Blink! Blink! SONOFF Product is Talking to You
SONOFF · 2026 · official_doc
- 2
SONOFF · 2026 · official_doc
- 3
SONOFF · 2026 · official_doc
- 4
SONOFF · 2026 · official_doc
- 5
SONOFF · 2026 · official_doc
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