That latch unit uses four linkage rods. The inside and outside handles each have their own linkage rods, and the inside lock knob and outside lock cylinder each have their own linkage rods. Since neither lock operator is apparently working, I'd suspect that the latch mechanism is locked out, and that may be due to one of the latch handles (inside or out) not being fully released. If the latch is not fully released the lock cannot be actuated. If you've ever have that little parking lot "battle" with your spouse / friend ("Let go of the handle - Unlock the door first...) you'll understand how the mechanism works. Make sure both the interior and exterior handles are fully released, then try the lock knob(s).
You might have a chance of observing part of the latch mechanism and linkages of you roll the window down and spread the lower glass sweeps to peer down into the door with a good light. Pulling the interior door panel with the door shut is no treat.