Plumber turned off the water main to fix a leaky pipe in the kitchen, when he finished and turned the main back on, one toilet in the house will not fill and has no water at the valve. What could the problem be?

Have you checked to see if there is water at the valve ? I have seen the fill system clog up esp with older pipes

Yes. I disconnected the line from the wall valve to the toilet, and there is no water pressure in that line when I open the valve. Faucet fixtures in the same bathroom have water pressure.

Yes. I disconnected the line from the wall valve to the toilet, and there is no water pressure in that line when I open the valve. Faucet fixtures in the same bathroom have water pressure.

Yes. I disconnected the line from the wall valve to the toilet, and there is no water pressure in that line when I open the valve. Faucet fixtures in the same bathroom have water pressure.

You are only about 2" from fixing the problem. It is likely the debris broke loose when the main was closed and opened. the debris gets caught in the firts valve to open and in this case it is the stop cock below the toilet. You confirmed there is no water in the line between the tank and the "wall valve", next step is to remove that "wall valve" which is actually called a stop. The debris can likley be ckeared by flushing water back wards through the valve or even a blast of compressed air.

Turn off water to house, open a faucet to relieve pressure. Remove toilet stop valve. Clean or replace, only cost about $5.