What error do you see when you try to log in to your Microsoft account on PS4? We can take a look and provide some further instruction or clear up any confusion. ^IV

Can you send a screenshot of that error so we can look into this further for you? ^BT

Once a Microsoft account has been linked to a PSN account, neither of the accounts can be associated with a different account. Unlinking accounts will cause your purchases to be returned to the original Microsoft account and will no longer be available on the PSN account. ^TK