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 Play Portal, the Jamstik App, OR with a combination key, on the D-PAD, of "Enter + Right".
In the Online Play Portal:
First, navigate to the "Open Play" section of the Portal.
To learn how to change the MIDI mode via your hardware or in the Jamstik App, please watch this video: