Try another output source and see if that helps at all. If not, check your settings. In AmpliTube you can create a new project to reset a majority of the app settings. Once done, if you still have volume issues, poke around deeper. There are a bunch of volume controls you can use to get a loud clear signal from your iRig 2.
If you want to make sure everything is set up properly, you can check with the support team here:
https://www.ikmultimedia.com/contact-support/