XB8 gateway user and password don't work

I have been using Xfinity at the same location for almost 15 years and always had the same user/password to log in to the gateway (10.0.0.1).

I had gateway XB6, then a few months ago my HOA (we receive xfinity through them) told me that we must upgrade it to receive the higher speeds.

I upgrade from XB6 to XB7 and the same user/password worked ok (seems like upgrading device transfers the settings, including user and password to the new device).

The XB7 had a noise problem so I requested an upgrade and got the XB8.

After installing the XB8, it is working ok however the user and password to access the gateway don't work. It keeps saying that the credentials are wrong. After 3 attempts it locks me out for 5 minutes.

Having used Xfinity for so many years, I have many settings configured in the gateway (these setting are not available via the xfinity app), as well as many fixed IP devices defined. So, resetting the gateway is not an option since it would clear up everything and mess up my network.

I've tried using Mac OS, Windows, Linux and android and using Chrome, IE, Firefox and other browsers and always the same problem.

I've disconnected the gateway and reconnect after 10 min hoping that would help but didn't resolve the problem.

Is there a way to reset just the user/password?

I've tried both the user/password that I had setup in the previous devices and also the ones posted in the xfinity website (user "admin", password: "password") and also the ones printed in the label attached to the gateway. None works.

Please help