When fixing my running toilet, I shut off water to toilet by turning shut off valve off. Now it doesn't turn back on! It turns fine, but no water is coming out to the toilet tank. I see the similar question answered a while ago (https://www.askmehelpdesk.com/plumbing/toilet-shut-off-valve-wont-turn-435930.html), but for the different configuration (mine looks like diagram 2). What to do? Thanks much.

It may be the stop valve itself and not the fill valve. Disconnect the tube between the tank and the valve, slowly open the valve to see if you get water. If you don't then replace that valve. If you do get water then the fill valve in the tank is in question

It could also be sediment in line, turn the valve off and on a couple of times to see if this clears it.

These valve handles are notorious for corroding and then spinning. Make sure the stem is turning, not just the handle.