if Input.is_action_pressed("Jump"):
# floor jump code not quoted for clarity
elif is_on_wall():
if Input.is_action_pressed("Right"):
velocity.x += impulse_strength
This will only trigger if jump and right are both pressed. Perhaps this is fragile.
Try putting print statements whenever you press either button (at the top of the script) and print statements inside those nested ifs to see if it is making it there.
Also, there was a similar question which was asked recently and the answer involved using the wall normal to determine wall jump direction instead. Take a look