Did you do anything in your Illustrator application folder? Removed something?
You could check if the file is still ther: locations of settings https://www.vektorgarten.de/illustrator-settings.html
Did you at one time edit the arrowheads file?And maybe saved your edited version in the plugins folder?
Maybe it got corrupted. You could try and just open it - does it still work?
If nothing helps, try and rebuild the preferences. This will destroy all your settings. https://helpx.adobe.com/illustrator/using/setting-preferences.html
If that also doesn't help, you would need to uninstall, run the Adobe Cleaner tool and reinstall.