Amplitube iOS failed me

I really like using Amplitube 5 as a plug in for Garageband and had even used Amplitube iOS to get good tones during zoom lessons. I tried to use it at a gig and it failed me :(. If you have any ideas please comment below. Thanks.

[@digitalchris6681]

Confirmed, using exactly same kit. With AmpliTube output levels set to just below clipping, and my amp input turned FULL ON (with great trepidation) I get a whisper. But a very distorted whisper with a massive lag (like 1 second).
Conclusion: the IRig USB amp out socket doesn't work.