Why isnt it passing the t mobile screen?

If your phone doesn't work after a factory reset, that suggests something went wonky with the OS partition.  T-Mobile may or may not warranty this (especially depending on age of device).  If they do, you'll get a refurbished device (which, based on forum threads may or may not be better).  LG may or may not warranty as well, depending on the age.  They'll repair your actual device and return it.

If you have no warranty available, the official answer is "nothing can really be done."  The unofficial answer is "you might be able to flash the original OS, depending on what is required to do that" -- you'd have to search other communities for that as it risks bricking your device and is NOT supported by T-Mobile (I don't even know if this device can even do it)