Then something is wrong with the database that can’t be fixed by AdRotate using basic maintenance.
If you a new/small setup you can choose to delete the plugin and start over, the new database will work fine. You’ll loose all AdRotate data though.
Or you can try and figure out what’s wrong with the database and fix it. I can do this as well for a fee. If you want me to take a look and fix things you can email me using the contact form where we can discuss this in much more detail. https://ajdg.solutions/contact/