I'm having the same problem. Almost every day the lte extender goes offline.
I reset and it comes back up but I'm not sure what's going on.
Often you get 4 bars and it shows you are connected to the extender #48 also shows connected to the extender, but incoming calls and texts fail.
Turning off Wifi on iphone XR IOS 14.7.1 and then back on, sometimes reconnects, but the connectivity has been very unreliable.
Plain old wifi calling sometimes works well and othertimes fails, which is why we bought the extender for nearly $300.
Any suggestions Verizon?