Was it working previously? No other changes, like a new crank? Did you do any shifter or cable maintenance just before it quit?

Post a clear photo from above the bike and another from the side, and a third from the front or back would be good.

I can move my triple derailleur by hand. Both thumbs on the derailleur body, near the top. Pull on both index fingers behind the cage. It's a strong spring, but not too difficult to move.

(The Park Tool Help suggests wrapping a rag around the downtube part of the shift cable, and pulling it out by hand to move the derailleur to the big ring.)

Either:
1. Something is blocking the movement within the derailleur.

Verify you are adjusting the High limit screw:
The High limit screw keeps the derailleur from moving too far outward. You can see the tips of both limit screws. They both hit part of the derailleur body to stop the movement in one direction, and you can verify which one is High and which is Low by seeing when the ends of the screw is about to touch.

Maybe something broke in the derailleur body. But then, the shifts between the middle and small chainrings would probably have trouble too.
Is the cage loose at all if you wiggle it?

or

2. A crankset problem, where the chainrings have shifted outward. This seems very unlikely.
Is the crank loose if you grab the crank arm?
Do the middle and small chainrings still work the same?

Adjustment

Follow the Park Tool Front Derailleur Adjustment steps. Don't skip a step, start from the beginning. See if that helps!

I really like the Park Tool repair pages. They don't assume you have experience, and explain each step.