I have a series 3 on Tmobile with an iPhone X, both on the latest software. Frequently, but not always, when I leave the phone at home and am out with my watch, I don't have any LTE connectivity and there is the red X at the top of the watch home screen. Sometimes, rebooting the watch helps, but many times that does nothing. I erased the watch and restored, but still having the same issue. I called Apple and they say to call Tmobile, who I am sure will ask me to call Apple. Any ideas?