Well, I had the same issue. Noticed in late Jan. early Feb. LG G8 ThinQ. Purchased in 2019 through XM. After hours wasted with tech support, they insisted on sending a new SIM card. Unfortunately, they can't send it to any address but the primary account holder's, which is my father's who lives 2 hours away. I have no car, so he had to mail it to me. Ended up taking about a month for me to get it. Still had to get tech support to help, but eventually got it working again.

I tried everything to change the APN as that seemed to be the problem. No one could change it. The phone is fully paid for & I'm still paying insurance on it. I went through the steps to unlock it, but still couldn't modify the APN.

Just noticed today that mobile data no longer works. After reading all of the recent posts on this thread I refuse to ever buy a phone through XM again. I would rather have a stock phone that the manufacturer could assist me with rather than a phone XM will restrict & load with bloatware. I'll never buy another phone that won't let me create new/modify existing APNs. Very disappointed.

Not sure what to do now as I've paid for the phone at least twice over because of the insurance.