I've been having this issue as well with XYZ 2.0A Duo.
@horst There's not a lot of troubleshooting you can do. It typically happens to me with larger files.
I find that to get the printer to work at all I have to perform a certain dance.
1. reboot printer
2. unplug USB from computer
3. launch S3D
4. plug in USB cable to printer
5. open a model/position/process preview
6. open machine panel and manually connect (it defaults to bluetooth for some reason--I need to manually select USB)
7. once the machine control panel is communicating with the printer (communication tab will live post printer state)
8. go back to the preview window and click print
Even doing all of that, I can only reliably print small files--like a test disc of 1cm x 3mm. Printing larger files will be a 1:5 crapshoot. Sometimes just repeating the process above works. If it fails more than 3 times in a row I can sometimes reboot the whole setup--computer/ printer and get it to run. But, it is not reliable.