How to Fix Sonoff Device Not Rejoining After Power Loss
- Router not up when the device powers on
- New DHCP IP after the outage
- Device reconnect timeout
Problem Description
After a power outage, your SONOFF device does not come back online in eWeLink. The LED may be blinking rapidly (pairing mode triggered by power flicker), or the device boots before your router is ready and gives up trying to connect. Older models like the BASICR2 are especially prone to this because they do not retry WiFi connections indefinitely after a failed attempt.
Why This Happens in Real Homes
A SONOFF that doesn't rejoin after a power loss usually powered back on before the router was ready, or got a new IP when the network recovered — so it couldn't re-establish its cloud connection and stayed offline. It's a reconnection-timing issue, common because devices and routers often restore power at the same moment.
Reserve a fixed DHCP IP for the device so its address is consistent, and after an outage let the router fully boot before power-cycling the SONOFF to force a clean reconnect. Improve 2.4GHz signal at the device and disable band steering so it lands on the right band. Update firmware for better reconnect handling, and re-pair if it stubbornly won't come back.
Symptoms
- Doesn't rejoin after power loss
- Offline after an outage
- Won't reconnect on power restore
- Stays offline post-outage
- No auto-reconnect
- Needs re-pairing after power loss
- Offline until reset
- Recurs after each outage
Recognize these? Here's what usually causes it.
Common Causes
- Router not up when the device powers on
- New DHCP IP after the outage
- Device reconnect timeout
- Weak 2.4GHz signal
- 2.4GHz radio slow to return
- Band steering re-sorting
- Firmware reconnect issue
- Power-on state/config
Most fixes happen in the first 3 steps.
Do not factory-reset devices before verifying network-side recovery sequence.
Tools & Requirements
Step-by-Step Solution
Check if the device is stuck in pairing mode
After a power outage, some SONOFF devices (especially BASICR2 and older models) enter pairing mode instead of reconnecting to WiFi. The LED blinks rapidly (2 blinks per second) instead of showing a solid light. This happens if the power flickers multiple times quickly — the device interprets the rapid on/off cycles as button presses, triggering a factory reset. Newer models (BASICR4, MINIR4) have 'power-on state' settings that prevent this. If the LED is blinking rapidly: re-pair the device in eWeLink.
Set the power-on state to keep last state
In eWeLink, tap the device > Settings > Power-On State. Options are: ON (always turns on after power loss), OFF (always stays off), Keep Last State (returns to whatever state it was in before power loss). Set this to 'Keep Last State' for most devices. This setting is stored on the device's flash memory and survives power cycles. Without this set, the device defaults to ON, which can also cause issues if the device turns on but fails to reconnect to WiFi before your router fully boots.
Check your router's boot time
After a power outage, your router and the SONOFF device both power on simultaneously. The SONOFF device tries to connect to WiFi within 30 seconds of booting. If your router takes 60-90 seconds to fully boot and broadcast the SSID, the SONOFF device times out and may stop trying. Most SONOFF devices retry WiFi connection every few minutes, but some older models give up and stay offline until manually power cycled. If this happens consistently: add a UPS to your router so it boots first, or use a smart plug with delay-on feature on the SONOFF device's circuit.
Assign a static IP or DHCP reservation
After a power outage, if many IoT devices reconnect simultaneously, your router's DHCP server can run out of available leases or assign a different IP to the SONOFF device. Some routers have a DHCP lease table limit (common on ISP-provided routers: 32 devices). Fix: log into your router admin panel, find the DHCP reservation or static lease section, and assign a fixed IP to each SONOFF device using its MAC address. The MAC address is in eWeLink > device > ··· > Device Info.
Update firmware to fix reconnection bugs
SONOFF has fixed WiFi reconnection bugs in several firmware updates. The MINIR4 firmware v1.5.0+ fixed a bug where the device would not reconnect if the router changed channels during the outage. The BASICR4 firmware v1.3.0+ improved reconnection reliability when multiple devices compete for WiFi association slots. In eWeLink, tap the device > ··· > Firmware Update. If no update is available and the device still fails to reconnect after outages, contact SONOFF support with the switch model and firmware version.
Quick Solutions
Still having issues? This is usually the deeper cause below.
If drain continues after replacing batteries, check the event history — a stuck-open sensor or rapid polling loop burns through batteries in days.
Post-outage validation should be part of reliability testing for critical automations.
Battery-related failures are almost always flagged too late — the device degrades silently for days before the app catches up to what's actually happening.
- Router not up when the device powers on
- New DHCP IP after the outage
- Device reconnect timeout
- Weak 2.4GHz signal
- 2.4GHz radio slow to return
Before you go — try one of these (they fix most cases).
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Official Manufacturer Manual
SONOFF provides official product documentation through their online manual rather than downloadable PDF. Access setup guides, troubleshooting steps, and product specifications for your Sonoff Post-Outage Recovery.
Source: sonoff.tech
Need More Help? SONOFF Support
Note: The contact information below connects you directly to SONOFF's official customer support team, not Trunetto. They can help with warranty claims, device replacements, and advanced technical issues.
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