I had this problem and fixed it, maybe the same will work for you?
So my poor internet connection kept jumping my phone out of home network and onto 4G.
You’ll see this when the companion app stops showing the map.
Your phone and laptop need to be on the same network for your laptop to talk to your sensors (unless it’s hardwired), so my laptop would lose connection and my zwift character would display 0RPM, 0Watts.
The fix is turn data off so 4G doesn’t kick in, there’s a quick button to do this with IOS, it’s the green icon (next to flight mode) when you swipe from top to bottom to bring the IOS quick menu up.
Before every ride I turn this off and since then it hasn’t happened / it resolved the problem.