What do you have plugged into the USB ports? May seem an odd question but it has been a known cause. Unplug everything from the USB ports, pull the power lead and wait a minute, don't put anything back in the USB ports but plug the power lead back in and try activate wifi using only the stock remote.Router is fine. All my devices are connected with wifi except for the neo T5. Even my firestick 4k in the bedroom is connected with wifi.
Wifi just cant turn on at all on the T5.