Unable to use T-Mobile Home Internet with work VPN, any suggestions?

I got it resolved by swapping out the Sagemcom and getting the Arcadyan device. Based on the timing of the other comments it seems like it was the latest firmware update that broke all VPN access. My tech support was clueless about the issue, she just said "oh yeah VPN doesn't work at all." I told her it was working for 6 months without issue and she had nothing to say to that. Thankfully I found this thread about trying a different manufacturer. So far the Arcadyan is working but its like 30% slower. We'll see how long this lasts before they push out another destructive update.

We use GlobalProtect and the MTU adjustment was only a temporary fix because every time I reconnected to the VPN the MTU reset itself to 1400. Need admin level to change the MTU so I couldn't do that every single time. Another work around was attaching a router to the gateway and changing the MTU in the router settings. Even though it connected, it was constantly briefly disconnecting so my large data files kept failing to transfer. If you can deal with these problems then the swap may not be necessary for you.