I have two Ap2Stream Pro V3, one connects fine to the WiFi the other does not.
The non functioning one, follow all steps, search device, slow blinking, select device, choose wifi network, enter password. It returns to select network. Repeated attempts same result, factory reset, same result.
Did you try to connect right beside the router? Mine would connect in a different floor but wouldn’t operate properly without a strong connection
I had a similar problem with my second Pro 3, it took 3 or 4 tries of inputting the password before it would connect. The signal strength was about 40% in the location of the unit.
My Wifi strength was high 60s and everything would work except for paid streaming like Amazon or Napster. Once I want wired or moved the box next to the wifi router ,(100%) it worked great.