After the sprint I got a boost button. When clicking, there is no “Watt” , no resistance on my ergometer.
The device connection is still on “connected”
I’m not sure about a boost button, but it sounds like you’re referring to a power up.
I’ve never known power-ups to cause the trainer power (e.g., watts) and resistance to drop out, so I have to wonder if it’s merely happenstance that your issue occurred at the same time that you got a power-up or used a power-up.
Looking at your setup, you have some superfluous data (e.g., old trainer data) in your prefs file, which can sometimes result in odd or buggy behavior of your paired devices in Zwift. I’d suggest that you delete the prefs file and knowndevices file, then try another ride to see if the issue goes away.
For info on how to reset your preferences, see this article.