Already checked the starter. And got multiple batteries as well as jump leads on another vehicle

Put a new battery on it due to previous owner hadn't charged it and run it dry. Changed the starter motor due to it sticking

Took it on a 10 mile drive. Parked it up for 2 hours then when I went back to it it refused to start

Just wondering if anyone can help. My td5 won't start. It's had a new battery and starter motor. The starter motor engages but won't turn over the engine. It is as if the engine locks up. Any suggestions greatly appreciated