last 8 of the serial number?

72341982

i meant try using the last 8 of the serial number as the password. 

Thought that’s maybe what you was saying. I tried that to and didn’t work either. I need to get to the setting and change to bridge mode. I already have a Erro that will take the place of the built in router in the Arris. I used to be able to a factory reset by pushing the reset button on the modem-router and then use the default user name and password. After I try to reset it now it says to use the security key on the bottom of the router for the password but that doesn’t work either. Appreciate you trying to help.

I’ve seen some resets not go through. Did you push the reset for up to 30 seconds while powered on? 

Only about 10 seconds.