I have several newly-installed smart dimmers that can't connect to the wifi.

The wiring is good and the dimmers work manually.

The blinking amber/green is working, and while trying to add a new device, the app recognizes that I have various devices ready to set up, and is able to connect to them (via their temporary wifi, I guess).  Then the app times out while trying to connect to the wifi.

I followed the instructions and configured my 2.4GHz wifi to use channel 1 (and 6) with bandwidth of 20MHz.

Still the same result: pairing failed.

I was able to set up various previously-installed dimmers successfully so I bought more dimmers, switches, and sockets.  Can't connect any of the new ones.

Any ideas what could be the problem?

Thanks