Cannot login to router

Hello,

I have the Cisco DPC3939B router. The "cusadmin / highspeed" login does not work, it says "invalid password." I tried a factory reset, which seemed to reset the device, however "cusadmin / highspeed" still results in "invalid password" as before.

For what it's worth, I've never logged into the router since starting service last year.

Is there something that you could do on Comcast's end to reset the password? Thanks,

John