We have moved the webi reports from BOXI 3.1 SP3 FP3 (22.214.171.1241) to BOBI 4.0 sp6 (126.96.36.1996) and in BOXI I could add the detail fields to the report while in BOBI when i try to add it says incompatible objects for the exact same report.
The backend database is SQL Server
The incompatible object problem might be caused by universe joins or aggregate navigation or security rights. As you have migrated reports and universe. Its better if you check if universes are properly migrated or not.
You can do following test case:
Try to create a new report from universe which is giving incompatible error. Also check if all the objects are having problem or any specific ones. Once you reach specific objects, you should be able to investigate further.
I hope this should help you.