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the most likely cause which is pretty common is that the door harness has broken wires.
you need to pull back the rubber loom that is in between the body and door and check for broken wires
If there are broken wire then the best fix is to replace the harness but you could try and repair them. the only thing is the repair will probably not last long due to the constant flexing in this area
As far as replacement this is also difficult because on the 06 access to the harness requires removing the inner door panel and outer door skin.
this picture is with out the outer door panel
If you would like to open your gas door before you get a chance to check and repair the wiring you can pull back the right side trunk trim panel. you don't have to fully remove it just enough to get your hand in there. Then you can get access to the fuel door actuator and pull the cable to release the door.
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