Pigletjohn radiator help please

[poshme]

@pigletjohn
Please help.
One radiator. Has TRV. Never gets hot. Tried bleeding it. Tube up to rad is hot.

YouTube suggests that th pin underneath the big white thing should move up and down. It doesn't move at all. I'm wary of pulling it as one chap said it might result in water everywhere!

Do all rad pins move? Is it possible I have a different kind?

Any brilliant advice?
(LPG boiler, rest of radiators get hot, pressure ok)

1. turn off ALL the hot ones. Does the cold one heat up?

2. photograph the valves at each end, with the knobs on, and off, if you can. Include any maker's marks.