Rm520nglaa-m20-sgasa firmware request and instructions. I'm lost

Hi, I just got an rm520nglaa-m20-sgasa and I can’t get it to connect to T-Mobile home. Every trouble shooting thing I see begins with updating the firmware, but I am clueless on how to do that.

Running ATI it says revision RM520NGLAAR01A06M4G

I’m using in it a GL.iNet M2 5G USB development board with a GL.inet router.

Thank you!

Dear @RobWilJas
I have sent firmware to your email, please check.