If you were supposed to connect BT products only then I think we would all be in trouble, I know I would be.
Is this the procedure you tried? if not then it may be worth a try. If yes then it only resets the microprocessor - by the sounds of it you need to reset the system firmware.
Have you contacted Marantz for ideas?
Have you seen this NB: it does say it could take several hours
Guess it must be a fairly common occurrence or Marantz wouldn't have produced those instructions. ☹️
My thoughts exactly. It's not the same model as the OP was asking about but they're probably not so different
It sounds like you've bricked it then. You could just leave it powered up overnight and cross your fingers, toes and anything else you can cross - you've nothing to lose