In the highest gear, check that there is tension on the tensioner cable and therefore that there is chain tension.
In the highest gear, check that there is around 1cm between the vertically-oriented section of chain and the section of chain over the tensioner pulley.
In the lowest gear, check that the derailleur can’t move further inboard, meaning that the low limit screw contacts the derailleur link.
Check that the chain correctly meshes with the narrow-wide teeth of the derailleur pulley.
Check that the tensioner pulley is aligned with the chainring.
Check that the derailleur cable is seated in the channel on the derailleur link with the cable clamp bolt.