There are 2 belts.
The transmission belt is tucked up high where it is hard to see and harder to get sticks & stones to.
You really have to pull off the deck, get uder the mower, put the brake on ( makes the drive belt slack ) .
Mark the belt with a white marker then run it completely around and check for missing lumps.
You will find it a lot easier is you drain the fuel tank , sling the engine by the front axels and stand it vertical.
While it is up check all of the little pulleys, the action of the clutch/brake