I have the same problem, all apps and iOS are up to date. What I notice on the audio track in Cubasis that has Music Studio as input, it’s missing the ‘Monitor Recording’ control/icon which is usually next to the ‘Record Enable’ control. I even manually created an audio track and initially, it has the ‘Monitor Recording’ control but once I add Music Studio as input, the ‘Monitor Recording’ control goes away. This must be the reason why I can’t hear audio from Music Studio.
Just like what have mentioned above, Music Studio monitor output works with Garageband via audiobus. I also tried Animoog with Cubasis via audiobus and monitor works. Thanks, -Fled
iPad Air iOS 8.1.1
Music Studio 2.5.2