Cannot figure out router default admin login, even after a hard reset.

I cannot login to the admin settings for my XB8 router. I have enabled admin login through the xfinity app, and performed a full reset by holding the WPS button for 30 settings until the light blinked green. The default login of admin/password hasn't worked, neither has admin/admin, and there is no admin login information on the router's sticker. The model number is CGM4981COM. I'm trying to enable bridge mode, so I need access to the admin settings page.