While the bike is off, I placed a gauge on the valve stem and it shows 0, I tried to pump some air in with a hand pump but could not.
No, it doesn't pressurise itself.
Probably a small leak somewhere, the volume of air the forks hold is very small. Get one of those generic spray bottles, fill it about 3/4 way full with water then add a tablespoon or so of liquid dishwashing detergent. (Hand washing stuff, not for an electric)
Lightly shake it up, then liberally spray it on all fork seal areas and especially all the upper stuff.
Now try your hand pump looking for any bubbles.
You may have a simple Schrader valve that's given up the ghost and I think they're the same as the ones that go into tires. $2 tool, tire place will give you a valve or two for free.
Start there, but as mentioned don't use anything more than a hand pump lest you blow your forks apart.