Sprint former costomer that cant use t-mobile app/site.

I was with Sprint on a family plan before the merger & i got well ahead of the game with the sim swap. I have a iPhone 12 Pro & i switched my Sprint sim over almost a year ago if not longer due to service issues with sprint sim card. I even recently got another t-mobile sim when they offered it for the rest of our lines but we still can't long into the t-mobile app or website. i keep getting an error or page never loads. The sprint web site seems like someone made it on github recently it's just horrible no matter if i use a pc or iphone you can hardly navigate the preferences & permissions page. Why is it that there is constant error during sign in after using verification code page will get 404 error so will have to go back to login page re input same code and page work. Seems to be a security problem, in my mind that should not happen almost every login. I'm just wondering if anyone else has experienced this or if there is any info when we can all use the main t-mobile site. My girl just upgraded to the iPhone 13 through & she still we can't use there site & the apps we can use are have use able at best. Sorry for the rant just looking for insight it was a pain even being able to make a account to use this community but still can't use email for website and i even have a T-money bank account with any-mobile i'd but no cant use the t-mobile site/app, Just a hacked up a$$ Sprint site lol.