i keep trying to downgrade my icloud storage but it won’t work

This is primarily a user-to-user support forum; other Apple users like you. See the instructions in Downgrade or cancel your iCloud+ plan - Apple Support including the following if necessary:

If you can't tap Done, make sure that you're signed in with the same Apple ID that you use for your iCloud+ plan. You can also try following these steps on a different device. If you still need help, contact Apple Support.