Hello @l.pricop
Some businesses and individuals have multiple accounts - one for corporation tax, one for VAT, one for self assessment, etc.
The most common cause of this message is the wrong account being linked.
I would completely revoke it (on both QuickFile and HMRC), and relink it as new.
Here is another similar post from the forum
If you are sure all the details are correct and you are still getting the error message you would have to contact HMRC directly as it is not something we have control over.
All we do is try and log into your HMRC account in the background using the details you provided. The errors are returned by HMRC