GarageBand external audio not exporting to MP3 on iPad

When exporting a GarageBand project on iPad to the app voice recorder 7 (in order to convert to an mp3 file) the external audio I’m using on the track (synth one J6) unloads and the track is exported without the synth.

[Re-Titled by Moderator]

Original Title: how can i export a project on garageband that contains external audio software to mp3 on iPad