I’m currently unable to access my collaborative project, I’m receiving a “Cannot Download Entry” error which the log indicates is due to a URL 401 error. The log can be found [88221-editor.txt|88221]. Is there a solution to this issue or is it a server problem?
I also had the same problem but solved it.
Close your unity.
Go to your Project Folder >>> Library >>> Collab
you will find Collab folder delete that folder.
Open unity and you can collaborate easily.
Same here… 
have the same problem