Usually in BlackSquare products the GA button functionality depends on what GNS unit you have installed (and thus which autopilot is working under the hood), but in the case of the Caravan, there's no flight director, so GA mode doesn't do anything.
@Bigmarty Thank you so much for replying with your solution! I was unaware of this mapping, so I might be able to help users in the future who encounter this issue. Thank you!
@miller39687 Excellent! Glad my guess was at least somewhat accurate. If it's anything less than obvious, please let us know in case someone googles the same question in the future. One of the reasons I like this forum so much is that it appears very high in the Google search results, which hopefully makes solving problems easy for my users.
That was it. It never occurred to me to look in that section of the tablet. And there it was COVERED. Had to start the aircraft up many times to check it out after removing the covers. Thanks to whoever posted that.