I found to have success if I follow a very specific procedure in getting everything connected.
Before I even open Zwift, I do the following:
Open my Profile on the PS800.
Press “Connect” under “Connect devices?”
Press “Pair” under “Mobile App”
Now I open Zwift, select my user, and “Tap to Pair” the speed sensor. After a second, the PS800 will show up for me to select. I can then select my route, workout, etc, and press Run.
If I follow this procedure (placing the TM in pair mode before launching Zwift), I have found that I can reliably connect to Zwift and that my avatar will properly “move” once I’m loaded. I do seem to experience, from time to time, that Zwift “remembers” a prior speed and as soon as I’m loaded into the world, my avatar is already moving at 0.5 and the clock is ticking even though I haven’t yet started the TM. Minor inconvenience…
I do feel like this experience should be easier. I have heard/read that the problem is that since the tablet is portal it doesn’t remained “paired” or “connected”, and that folks who use another means (PC, Apple TV, etc.) might just have it easier.