router password won't reset after router reset

I have an xfinity supplied and branded Arris TG862G/CT modem/router, whose admin page is accessed via 10.0.0.1. The support page on both Xfinity & Arris' website says the default username and password is "admin" and "password" yet when I try that it says I have the wrong password. I have used this combination to successfully log in in the past. I have reset the device several times via holding the reset button as well as unplugging it. There is a lockout if I get the password wrong 3 times in a row. Resetting the router will reset the lockout count but does not actually reset the password