Engaged PTO lever on mower and began mowing but shortly thereafter mower stopped. 48' deck has New belt and properly connected. Replaced PTO switch behind lever but no help. Mower makes no sound or apparent attempt to engage when PTO lever engaged.
I'd start checking the safety switches for starters.
Then trace down the circuits to see where (and when) there is power. Track it down before replacing parts.
Do you have, or would consider, the tech manual?