Hi,
I just installed both the AC7 Core on my iPad and the AC7 Core Mini on my iPhone. Both of them connected but I did have a bit of a time getting the AC7 Core Mini to connect and it appears the reason was because I needed to restart the rtpMIDI service. Once I did that, it found my device and then everything worked fine.
I did not have any issues with the AC7 Core though. What I did was the following:
1) Installed the App on my iPad
2) Installed the rtpMIDI service
3) Selected and added the iPad device from within the rtpMIDI GUI
4) Enabled the PC running Sonar from within the rtpMIDI GUI
5) Started up Sonar and selected an existing project. This project already had the V-Studio 700 setup as a control surface
6) Added the Mackie Control surface to the project and made sure both the Input and Output were set as the PC running Sonar
7) Applied the changes and exited from the project settings
8) Selected the Mackie control surface
9) Started the AC7 Core App on my iPad
10) Clicked on the mode button until Sonar Mode appeared right above where it says master volume
11) Clicked on the Reset button
After that I played some of the project, moved faders etc... It even worked with my V-Studio 700 and controlled all the faders on the console.