A toilet that won’t refill after flushing typically has a faulty fill valve or closed supply valve. Check that the shut-off valve behind the toilet is fully open. Lift the float arm inside the tank to see if water flows. If not the fill valve needs cleaning or replacement. Debris in the valve can block water flow. A kinked or disconnected supply line also prevents refilling. Universal fill valves fit most toilets and cost under 10 dollars.