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Sonoff Switch Pairs but will not connect to WiFi

After Successful pairing and Renaming the device it does not connect to wifi and Green light keeps blinking, tried to delete and repair but no luck.

One device is connecting and another - Does not.... :( 

75 people have this problem

Thank you, Franky!

Registered here only to say that!

I disabled "Short Preamble" and "WMM Mode" in my OpenWrt and my TH16 finally connected!

Other settings looked ok:

DTIM Interval - 2

Mode - N

Width - 20MHz

RTS/CTS Threshold - off

i've seen the thread is very very old, but newest entry is only 17 days ahead.

So i've got also the problems with the Sonoff T1 (3gang UK Version) to connect to my new
Edimax RA21S Accesspoint. I had previous the Edimax 6808 V.2 which work pretty well, also with T1.

Sonoff Basic, 4CH, Wemos D1 Mini, ESP8266-1, ESP32 aso.,  all are working well.

Only the T1 won't connect.

I found now out why.
Its the Wifi "preamble". It can be set to "Long" or "Short"(default).
Set it to LONG and the T1 can connect.
Well some AC can't be configured this details, but if, try it.
It should be:
LONG preamble
20MHz Bandwith 
WPA2 mixed (sometimes only AES work?!)
DTIM Period 3 (mostly its 1 as default)
Beacon interval 100
CTS Protection disabled
WMM disabled

and i also found (i don't realy know why this matter), but if  5GHz has the same SSID
it won't connect. Dont ask me why.

Hope that helps a bit out of a 3 year old (long)  thread.

all the best

had the same issue with netgear r7000 and L1 led strip. i tried a lot of stuff including changing SSID, disabling 5ghz band, disabling nat/qos/whatever. 

it must be something with a router 'cuz LED controller goes online without issues with android, iphone and even laptop hotspot

finally, the solution that worked for me:

1. disable 2.4ghz radio on router (or power-off router)

2. create wifi hotspot on smartphone with exactly same SSID and password as router's 2.4ghz network. just make sure you're not using the same smartphone for hotspot and pairing

3. pair device using different smartphone, wait until device goes online. i used compatibility mode for pairing (btw, had to disconnect led strip from controller to enable it)

4. disable hotspot and enable router 2.4ghz band

right after that i got an error on controller (blinking twice per second) but after ~5 min controller went online, and so far everything is ok

Set smart scenes to control devices by temp. & hum: working with sonoff temperature & humidity sensor (am2301, ds18b20), sonoff th10/th16 can detect the real-time temperature & humidity of the environment and set up a temperature/humidity condition to control connected home appliance, even the ones connected with other sonoff products, such as sonoff, sonoff rf, sonoff gba emulator ios

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It looks like problem was solved with old LG Nexus phone... unbeliveble

That could a problem. I have top TPlink Archer 11000 router. Funny storry, TH16 connected without an issue.  T0EU2C-TX and TH10 had an issue

As my experience goes I had similar problems.  Repeated attempts all  endned up as failures. All I did was switched to my tablet after logging out of eWelink application on my phone. It linked & connected to the router without a problem. 

It might even be a problem with the router. Some of my Sonoff devices simply would not connect top my main TP-Link router. When I connected a Zyxel travel router to the TP-Link as an access point it connected on first attempt. It is maintaining VERY steady connection now. BTW I am supplying 9V power to the router over POE near the cable modem.  Can't figure out why that both are so close together but works with one but not with the other. 


I have the same problem with T0EU2C-TX. Had tried everything, and after successfull pairing, the device is not connecting to the router. The led is blinking slowlu (1/sec) and nothing is happening. 

Helo all, i have solution of this problem. You must change wifi setings on your router, in 2,4ghz radio set "Legacy" mode check b/g protect then pair and connect sonoff switch to this WLAN and update FW. Next set your router to "auto" mode b/g protect must by checked. This solution i tested on Asus AC58U and AC59U V2.
I ran into the same issue, I had two problems in my setup. 1- the network I was using was on 2.4 and 5.8 GHz. Once a physically isolated network created for the SONoff the devices connected perfectly. 2-the other bug I had was that the SONoff was reminding it's last wifi connected on even after a reset to default. I had to create a network with the same SSID and Password previously connected, then unpair the SONoff. After that the pairing process was working as described in the documentation. Hope it helps!

I had this issue with a new ZB Bridge but was able to get it connected by temporarily disabling the 5GHz channel on my router.

Once it was connected and added in full I re-enabled the 5GHz channel and the ZB Hub has worked fine ever since.

It seems I found the solution.

This is for the case when devices pair but do not connect to wifi then.

First of all check for already known troubles - must be no special characters in SSID or password, no 5GHz network, 2.4GHz must be b/g/n etc.


1. remove unconnected devices from your main account in ewelink.

2. use alternative device (I used iPad instead of iPhone for this) and install ewelink there.

3. register new account. if you have no free email you can use any service for temporary mailbox like etc.

4. add the device to the account using quick pairing mode. then check and update the firmware if necessary.

5. remove the device from the account. it should begin blink like ready for quick pairing mode

6. return to your main device/ewelink account. pair the device in compatibility mode. no need to unplug/plug, just keep the button pressed until it begin blink rapidly.



 If the Sonoff problem does not pair, check on the eWeLink app that the selected pairing mode is consistent with the blinking frequency of the LED on the device: ● If the LED flashes alternately twice fast and once slow, you must use the Quick Pairing mode (default).

Hi guys. I’ve had 1 sonoff switch for a while. Decided to add a second. Had the same issues as you guys and have been scouring through this thread looking for solutions. In the end i deleted both devices and stared again by pairing multiple devices at once. It found them both instantly with no messing with my router. I then re paired with Alexa and it works perfectly. Simple answer. Delete all devices and Just start again. Hope this helps.
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