New Chain,New Cassette,New Rear Wheel... Need help!

[Paulus]

I had something similar on one of my bikes. A new wheel, but the same cassette. The chain jumped of of the largest cog at the back when first used and wouldn't drop into top gear. Slight adjustment of the limit screws was needed, but the indexing was fine other wise.

 

[Erasmus]

If it's just the high gear (smallest cog at back) giving problems, then the B tensioner screw might need adjusting (tightening) to push the mech away from the cassettes. Good luck, John.