The gear menu I was talking about is this:
This is where you can see which individual gear models you have installed, and which ones you don't.
From this image, you can see that there are separate menus, one for AmpliTube 3 (which for you should be fully unlocked), and also menus for officially certified models from our co-branding partners such as Fender, Ampeg, and Orange. These are not part of the AmpliTube 3 package, but rather later additions we have added to be purchased separately.
In this example, only 2 Fender models are purchased and installed. The rest are greyed out, locked, and otherwise unavailable. The locked models can be unlocked for a 48 hour trial period for free, or purchased with Gear Credits. Both are done through the new Custom Shop. Simply click the locked model you want to try or buy in the menu, and you will be taken to it in the Custom Shop application.
I hope this clears it up for you.