I've got five Sonoff T1 switches (4x 1 gang and 1x 3 gang)
They have been reprogrammed with a C app via Arduino, although I do get exactly the same issue with Tasmota.
The work great with my Netgear R7000P access point.
I have just replaced the access point with a TP-Link EAP225 and now i have issues connecting to the network.
When I power up/reboot the Sonoff T1s they show up in the TP-Link Omada Controller app, but don't get an IP address or have any speed listed in Rate column - so they are recognised, but don't actually connect.
Now for the weird bit.
If i take the front panel out of the switch and power it up (3.3v PSU) they connect straight away without issue. If I put the switch back together again i get the same problem back again - even if the whole unit is only a few feet from the access point.
I've tried adjusting settings in the new access point (even turning off the 5GHz network), but no change.
So, in summary:
1. Sonoff T1 connects ok to a Netgear R7000P access point
2. It doesn't connect to a TP-Link EAP225, unless the front panel is removed from the base and powered by an external 3.3v PSU.
Has anyone had a similar issue and is it fixable?