Working with an app from a different developer and getting unusual results in playability? Is the high E string the only one that is working? You may need to switch to Single Channel MIDI Mode.
This can be done in the online Learning Portal for Jamstik app or site, the Jamstik Control App on iOS, OR with a combination key, on the D-PAD, of "Enter + Right".
In the Online Learning Portal for Jamstik or Jamstik Control app for iOS:
First, navigate to the settings section of the app and toggle the "Single Channel Mode" control.