prepaid plan -- t-mobile app/account not working?

I was told the same thing back in January 2021, however, I just went into the app today (Mar 19) which looks/works almost identical to the website.  My issue is that my long-time prepaid service for $3 - 30 mins or 30 txt works fine and I was able to put in my next payment due for April.  My other "line" is the newer $15 prepaid plan for unlimited calls/text per mth and that one doesn't work in the app or online - clocks like a bad internet speed / interruption when trying to play a movie!  Truly endless!  it does give the menu dropdowns but when clicked gives me "Customer Not Found"! (which is probably why it's "clocking" endlessly!  I've called 3 separate times since Dec and support says they will "escalate it up" and try again in a few days!  well months now and it still doesn't work!! very poor reflection on a touted front-leading tech company! so, I'll have to call in a payment yet a 4th time which if the website or app worked for my line, it would be so much easier!!  I'll be actually writing them as well to see if anything can be done that way?