Thank you for the answer Aniket,nnThe model was originally built with Ansys 18.1 and ACT Acoustics v180.1, while now I'm trying to run it on Ansys 19.2 with ACT Acoustics v192.2 (the last apparently). However, I managed to find a machine having Ansys 18.1 were I installed the last version of ACT Acoustics (v192.2) and it works. So the version of ACT shouldn't be an issue.nI started a model from scratch in 19.2 (Harmonic Response) and yet I cannot apply any acoustic load (as the Mass Source), while the Surface Body is correctly recognized.nI'm wondering if it has to be with something regarding the way I import the geometry: it's designed in another software, then exported as .igis, imported and with Design Modeler I make sure that all the bodies belong to the same part.n