What does it do, get stuck showing it's connecting? It can be slow sometimes. You can also try logging in separately by heading to
https://cloud.chaos.com/collaboration/ in a browser. And if all else fails, it may need a ticket via
https://support.chaos.com/requests/new for further investigation.
EDIT - after logging in via browser, see if the upload works from the VFB. You can also of course use the browser and upload things manually too, not just as a work around here, but it would also enable sharing and commenting on, say, mood board or example images rather than rendered images.