Firefox 115.0.2 and T-Mobile
I upgraded to Firefox 115.0.2. Now I can log into my T-Mobile account. But when I try to access 'Bill & Pay' or 'View Accounts' I now get "Access Restricted" error messages. This is frustrating as I was able to do so before. Clearing Cookies and Site Data provided no relief. T-Mo support had me try in in Private Browsing, and it works.
I had an issue with a bank, and turned off AVG Anti-Track and it work. But no so with T-Mo.
What the heck is wrong?
Opaite Mbohovái (1)
That's interesting that you're able to access the site when using a private window. That usually would indicate an issue with saved cookies/cache since private browsing doesn't use the cookies and cache Firefox has saved in normal browsing.
I know you've said you've already tried clearing cookies and site data, but have you only tried doing this for the current T-Mobile site? It's possible there's some other web domain that T-Mobile is trying to access that's causing the problem.
If you haven't already tried clearing both cookies and cache for all sites, it might be worth a try. Note that if you do try this, you will get logged out of all websites — so make sure you have any passwords you need saved and readily accessible. You can find instructions on how to do it here: Clear cookies and site data in Firefox