Water shut-off valves not working can be a major problem. There can be many reasons your valves aren’t working properly. The first step you should take is to turn off your main water supply, then you can figure out why your valves aren’t working.
A stuck valve may only require a spray of lubricant. Spray the valve, let it rest to lubricate and then try to move the valve.
If the valve is partially closing, you will need to replace the valve.
If it’s leaking, this can mean the seal isn’t working. Try tightening the fitting and/or replace the washer inside the valve. If neither of these fix’s work, it is time to replace the valve.