Problem getting 3D when using the Moon Spatial Player app

Downloaded AVP-native "Moon Spatial Player" (MSP) in order to play my own Side-By-Side 3D movie collection in AVP. Uploaded the movie file to the Cloud and then downloaded it to the MSP app in Vision Pro using the "Files" folder. When I play the 3D movie that I have been able to store in the MSP app, the correct right-eye-view and left-eye-view are displayed in the AVP adjacent to one-another, which is to be expected. So, it would seem that the proper right and left views are now in the MSP app. However, when I then select "side-by-side" in the 3D menu (the choices are "mono," "side-by-side" and "up-down"), a single image is created but it is not in 3D. The app (or the AVP?) is only using one of the two eye views. As a result, the single image is the identical in both eyes (i.e., both lenses) instead of separate right and left eye images in each lens. Has anyone used MSP successfully with a side-by-side movie file? If so, can you suggest what I might be doing wrong?