20b4 sync doesn't start on existing project

I have uploaded a few additional video clips to an existing Black Magic Cloud hosted project. Now the sync will not start. It states that it has 3 files to sync, but the % stays at 0%. Not starting it at all whatever I try. I have reinitiated the proxy plus high sync (which I use), restarted DVR Studio, but to no avail. I have created a new cloud project and uploaded the same video clips there and the files are instantly synced to the cloud.
What can be the problem? And how to sort this out?
What can be the problem? And how to sort this out?