Hey UncookedPatato,
Just to clarify, progress is stored at the EA account level rather than on individual platforms like Xbox or Steam/EA app. You're not able to transfer progress between different accounts, but rather any platforms you have connected to an EA account will be able to access the content on that EA account.
Are you seeing the progress if you log back in on Xbox, or is it not appearing on either platform now?
If you're only seeing it on Xbox, it sounds like the account you're checking on the website (showing the Xbox link) is not the same one being used to log in on PC.
If you're no longer seeing that progress on either platform, that would point more towards an unlink at some point in the past and the support team would be best to check into the matter further to make sure the original accounts are linked correctly.