According to https://together.bunq.com/d/35022-haven-t-filed-your-taxes-de-fr-it-users-we-have-a-fix-for-you it should be active until end of June 2021. However it does seem that the code is not working.
Bunq support team, could you help out here, please?

And I also have the issue that it shows I’m having 3 notifications - even though there isn’t any. Can you reset this, please?