Ask him to text you a closeup pic of the socket from above, and also the tube pins so you can see if there's any damage or if he just needs to push harder with a little wiggle. If it's in focus and well lit you can zoom in like a microscope.
He can also video while he tries to insert so you can see what's happening.
I think the tube pins would bend on removal before the socket contacts could be damaged.
Try a different 9 pin tube in the socket.