Start with fuse 26 Central Locking
You can probably unlock it manually by sucking ot blowing air in the line from the Central Locking mechanism. From service manual page




8N - 44 POWER LOCKS - SERVICE INFORMATION
Open the access panel in the right rear interior quarter trim


panel.


2. Remove the pneumatic supply line (2) from the fuel door


lock actuator.




Note: Use caution when removing fragile pneumatic supply


line fitting.






3. Release the lock pin from the lock actuator by pulling the


handle (1) fully rearward.