Plugin refuses to deactivate

I’m trying to remove this plugin and it won’t deactivate itself. When I go to Plugins => Installed Plugins and choose Deactivate I get a message that says “Plugin deactivated” but PHP Compatibility Checker still remains active. If I manually remove the plugin I get a persistent error message that the plugin files are missing since WP still thinks it’s active.

I’m running WP 4.9.6. I’ve tried deactivating the 30 or so other plugins I have installed and every one works correctly except for PHP Compatibility Checker.