is it too late to link accounts.

Hey settal​,

Cross Progression is already active on all EA accounts, but keep in mind that progress is stored on the EA account level rather than individual platforms like PlayStation, Xbox, Steam, etc. Because of that, if you link your platform to a different EA account, you'll lose access to that progress. 

In this case it looks like your previous progress on PS4 must have been made while it was linked to a different EA account. While you've mentioned it's linked here currently, the EA account you're posting with has never launched Apex on a PlayStation platform before. Any PlayStation progress you had previously would have been on a different EA account.

You would need to re-link your PSN back to its original EA account to try restoring access to any missing progress. If you're trying to play on PC, you'd need to log into that same EA account from the EA app or link your Steam there instead.

Do note that if you've made progress on Steam since then, moving that Steam to a different EA account would cause that to be lost instead. Unfortunately there wouldn't be a way to combine progress from two separate EA accounts.