If you experience errorcode 3, it is because the sender has entered an incorrect social security number (SSN), that does not match the one on your NemID. Since the system is validating your NemID by matching the SSN, it gives an error.
You need to contact the sender and ask them to correct the entered social security number. Then you can try again.
If the error persist, do not hesitate to contact Penneo support by email at firstname.lastname@example.org or by calling 71999893.