If you have entered the PIN code for your MitID app incorrectly too many times, your app will be temporarily blocked for a short period. If you again enter the PIN code for your MitID app incorrectly too many times, your MitID app will be temporarily blocked, and you must create a new PIN code to unlock it again.
If your MitID app has been permanently blocked, for example because you suspected misuse, you need to reactivate your MitID app before it can be used again.