@z_big I would try changing the router password to something really simple, at least to test connection. Something with no special characters, just upper case and numbers. Are you still using the serial terminal in Simplify3D still to send the commands? Can you also screen shot the Router setup (obfuscate the SSID and password as necessary), maybe there's something in there?
Please also send M122 to the Duet and post the response, if possible.
Ian