Both receiver and phone talk to transmitter. The sensor itself cannot store data.
If you only use xDrip, you would issue start/stop to pass command to transmitter.
Once transmitter gets command to start, either device can read transmitter and get status/bg reading. So stick to using receiver only to do start/stop.
Your transmitter probably is now in stop status.
From receiver, check if it shows option to start. If yes, do start from receiver. But no start in xDrip.
After warmup, as long as phone is connected to transmitter in bluetooth, xDrip should see readings.
(Check event log if not. May need a start sensor in xDrip if it not getting readings after receiver is getting hem).
(My phone xDrip status says I started sensor 3/17/20, but my receiver (tandem pump) shows start on 8/17.)