From the console it keeps showing it's not licensed but a second click show it is.

 

Maybe same issue here. Suddenly we've got an error and cannot sync, but our license expires on 2019/5/30. 

Just in case we renewed our license and restarted MS, but still got same error.

Sync cannot run due to licensing problem; please contact [email protected] for assistance: Your license covers products released up to 2018/05/30, but the release date is 2018/08/05. Renew your license at http://360works.com/renew

 

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Our licensing server has crashed, so that's why you are seeing this. We apologize for any inconveniences or issues that this may have caused. We're taking this very seriously and working as hard as possible to get our license server running and stabilized. Let me know if you have any questions.

This morning after they resolved the issue on the back end I restarted Mirror Sync Server console resolved the issue..

Problem was traced back to a corrupt MySQL table that stores renewal dates. Running a repair operation on the table fixed the issue. Very sorry for the hassle.

The problem had been solved. Thank you.