My first guess would be the normals from your High poly mesh. Could you check those are not inverted? Your UVs could also be inverted and would be the reason of the problem.
If the problem persists, you can send me your Low poly mesh and your high poly mesh on this thread so I can dig deeper.
Please, do not hesitate to contact me if you need any more help.
Best regards,
Cyril Dellenbach (Micro) | QA Support Artist | Adobe