On my end, they paired fine the first time (Android). Yet I recently changed my WiFi router, and since then I have been unable to pair them.
The only thing that changed is that after pairing them the first time, I had accepted a firmware update.
Resetting (via the reset switch under the pace-plate) has no effect... my app simply does not detect any of the switches (I have 5 of them)
Same problem was at me too. What helped me, I connected the switch with another network (with another SSID(!), I used guest-wifi from my router). Then I deleted the switch again and connected without any problems to my normal wifi.