Timing problem

Did a head job on this vehicle.
Timing set had excessive wear so I replaced it. I set all the timing marks to service manual on first start runs one second then turns off. Crank again and now engine winds like it is free spinning. And throws a cam sensor fault replace cam sensor- no joy. Pull timing cover, chain is off crank gear. Probably my fault, I did not get it all the way on the shaft towards the block. Check everything again, idler gear had about 3-4 mm more to push on the idler shaft. All the marks look good, I button it back up, and it does the exact same thing. I have not pulled the timing cover, but the symptoms are identical.

Thoughts?