Try clicking on the Detail button, it should give you more details on the problem and it’s cause.

There is a troubleshooting page for version control in the Mendix documentation, so I would also suggest taking a look at this once you have some more details and see if the issue is listed there. 

If that fails, send a copy of the log (Goto Help → Open Log File Directory) to Mendix support.

https://docs.mendix.com/refguide/troubleshoot-version-control-issues/

Good luck!