Came across this issue the other day – ESET Endpoint Antivirus suddenly decided it didn’t want to work anymore. Opening it up would show a blank window and nothing else. Right clicking the green check mark in the upper right corner would bring up some options, but the didn’t respond when clicking them.
The fix? Well you can uninstall and then reinstall it, though that ended up resulting in needing to manually finish the uninstall. The other option, and a much easier and quicker option to boot, is to go into services and restart (or in this case, start) the ESET service(s). Once the services has restarted, then everything started working normally.