I use Aquamail Pro on my 2016 Amazon Fire HD 8 tablet (among other devices I own). I've had no problems, including an update just a few days ago to v1.13.0-722. I have installed files on the Fire tablet (including Google Play Svcs. and Store) to make the Google Play Store available to me, and have had no problem; this is how I've been able to obtain and maintain Aquamail Pro (and its key) on this device.
Today, apparently, v 1.13.1-727 rolled out (actually it's only shown itself to this tablet; my other Android devices aren't prompting for download of any new Aquamail version yet). Some problems developed immediately.
After downloading and installing the newest version on the tablet, I went to open it from the Homescreen of the device. It wouldn't open, and the tablet OS indicated that it thought the app had been installed on an SD card that wasn't available to it (there is no installed microSD card), therefore it failed to open. I can open the app through the Google Play app where it allows you to "Open" recently updated apps.
I tried uninstalling, and this indeed did remove the app, but not the icon on the Homescreen, which appeared grayed out (normally an uninstall would remove the icon). I reinstalled from the Play Store and the app shows as installed and I again can open from Play Store but not from the Homescreen of the device, where the app icon shows as grayed out.
Any idea what's going on here? There have been no updates to the Fire OS (which is currently at v5.6.0.0, a version of Android Lollipop 5) recently. But as I said I had just downloaded and installed v1.13.0-722 with no apparent problems.
Additional: I have NOT uninstalled the Aquamail unlocker key.
Wait there's more: I just uninstalled the unlocker and restarted the device; no change, grayed out icon still on Homescreen.
Hopefully I won't have to do a Factory Reset of the device. I may have to teach myself how to use ADB tools and that sort of thing, if I can determine the location and name of the icon's file, and remove it directly (with malice - lol!). I kind of doubt there are many users running Aquamail on their newer Fire tablets, but hoping for some good help and/or advice.
Later that day: I tried downloading (from here on the forum) and installing the immediately previous version, but even though it installs it would appear that the icon installed to the Home Screen remains dumb and grayed-out. As a function of the Fire OS setup it will serve to uninstall the AM app (long press and select to Uninstall - this is a bit different than straight Android where you uninstall from the "Apps" utility in Settings and the icon is removed as part of that operation. Or you can drag the icon, which is acting as a shortcut, to a "Remove" area without uninstalling the actual app.). But the icon will never open the installed app.
Interestingly on these tablets, there is another area of the UI next to the "Home" screen called "For You" where there is a "Your Recent Items" group of frequently used apps, and there is an AquaMail icon in that group that IS functional and does open the app. You can even select to remove the app or the icon from there, but it doesn't affect the grayed out one in the "Home" area.
I even got a microSD card to put in and see if that affected the device's idea of what it was dealing with, but AM won't install to it (I think that's well known), so no changes observed from that action.
I'll try to post a screen shot of the message for clarity. This is what has appeared ever since the download and installation of v1.13.1-727 via the Google Play Store. And keeps happening even when the app is uninstalled. Likely something corrupted as to the icon file's placement in the Home Screen, and to reiterate, the previous version didn't show this behavior.