The unit lives under the car, some are more exposed than others & will get weathered, some cleaning from time to time maybe required, wire brush, emery paper WD40 or a little grease if very dry.
Always fully load & remove the red key before use, & always refit the dirt cover when not in use.
If you can't remove the red key. Stop. Remove the neck and clean the contact surfaces of the neck & the receiver of grit, paint, surface rust, then try again. Cheers dale@towbarstrailers.com