Sumatra .25

Good clean fun repairing those.
Hopefully and fairly likely the fill valve is stuck, gummy or such. And you have soap checked everywhere right? Air gauge, other.
You certainly would desire the correct spanner wrench. IF you going all the way to the valve ( depending on skill level) maybe take a febw pictures.
Nice video which may or may not be in a language you understand but it doesn't matter.
https://www.youtube.com/watch?v=OcGAcmlFyTg

not my video.

Parts, PA will have them but all common O-rings you'll need should be at your local Ace Hardware ( if in the U.S.) and they'll be much less costly.


Keep us posted.

John