Erik Kostson
Ansys Employee
Are you using harmonic acoustic system or?
Also show all the loads and the whole analysis tree so I can see what you are doing - can not help otherwise.

As I said also wait/get (not sure if it is yet available as a student ver.) for the 2021 R2 version (coupled field harmonic 2021 R2) where this be much easier to do :).
Thank you