Refresh not working

Extensions -> Modifications -> Refresh not working
-- result : 500

Clear and Delete link is working but the Refresh going to 500 server error.
I'm using the latest opencart fresh install on nginx/1.11.8 (Debian).

Please ?

Could you post more information about the error?

List all third-party extensions installed.
Maybe there is a extension which is not compatible with your OpenCart version.