Hi 70709080004,
EA accounts can only have one type of account linked to them in their lifetime. This means if you had a Steam account linked up before, even if you unlink it, the EA account won't be able to connect to a new Steam account.
Our EA Help guide shares this:
When you link accounts, it creates a lifetime link to protect you from malicious activity and help prevent performance issues in your games.
You can unlink your platform accounts from your EA Account if you want to link them to a different EA Account, as long as that EA Account has never had the same account type linked to it before in its lifetime.
That means if you unlink an Xbox gamertag from your EA Account, you can’t link a different Xbox gamertag to it in the future.
This is why you're seeing that error message appear even though there is no longer a Steam account connected.
- EA_Lanna