There can be different reasons why your submitted proof of residence documents were rejected. Here are the most common causes:
The document is older than 12 months.
The full address is missing or does not match the account opening documents.
The document is not internationally readable. It must either be written in German or English or translated accordingly.
Which documents can you submit instead?
For tax residents or residence in Germany:
German registration certificate
ID card
Tax certificate
Electricity, gas, or water bill
Internet provider or landline bill
For tax residents with residence outside Germany:
Certificate of registration (not older than 12 months, with complete address including street and house number)
Certificate of Residence (issued by the local tax office abroad)