It's just really stuck. The recess Allen head is just an option, not a lock. WD-40 is not a good penetrant. You could try penetrating oil. More likely it's a matter of getting enough torque with the tool. Try placing the crank arm forward, find the wrench position pointing the wrench handle to the rear, as close to aligned with the crank as possible, put one hand on the pedal, one on the wrench, and push down. This works for opposite threads on both sides. You might need a bigger wrench if you don't have a pro model.