Turn off the water supply valve behind the toilet
Remove the tank lid
Check the flapper and chain for proper connection
Lift the flapper manually to see if water enters the bowl
Inspect the fill valve and float for sticking or damage
Adjust the float if the tank water level is too low
Clear any blockage in the toilet trap with a plunger
Use a toilet auger if the clog remains
Check the rim holes and siphon jet for mineral buildup
Clean or replace worn tank parts if needed
Turn the water back on
Flush the toilet to test it
Replace damaged parts if the toilet still does not work