Hi Martin,
I would suggest we continue here, there might be other affected user.
First of all I would like to let you know that, in any case, we will manage to upload your project. I am here to support you. 
So, let´s see where we stay:
You could create a new empty project in QFieldCloud, then you opened QGIS on your laptop and tried to upload your project with the plugin QFieldSync. But the upload wasn´t possible, right? Could you please share a screenshot or the message you get at this point?
Have a safe drive!
Best,
Zsanett
Imported from GitHub comment by @ZsanettMed on 2023-03-08T20:34:19Z