dunteachin, I just did the migration 5 minutes ago, and can tell you that following these steps will work:
1. Download and install on your new phone: (a) the Amazon app store and (b) the "regular" -- I'll call it Amazon Prime -- Amazon app. Ironically, you will need to download these from the Google Play Store. (I say "ironically," because I know you bought Touchdown on Amazon -- as I did, too!)
2. Open the Amazon Prime app, and click on the three horizontal lines in the top left corner of the app. This will open a menu of tabs on the left sided of the app. You SHOULD see, on the list, an entry for "Underground Apps." If it's there, skip to step 4.
3. If you're reading this, then there was no entry for "Underground Apps." To solve that, go to https://www.amazon.com/underground and follow the steps laid out there.
4. Click again on the three horizontal lines (at the top left corner of the app's screen) to open that same menu you opened in Step 2, and scroll down until you see the section titled "Library." Directly beneath that, you should see a link labeled "Your Apps." Click it.
5. You should see, near the top of the app's screen, three menus: "Cloud," "Device" and "Update." Select "Cloud," and you'll see a list of all of the apps you've bought via Amazon App Store.
6. Download and install both (a) "Exchange By TouchDown" and (b) "Exchange By TouchDown Key." (I installed the TouchDown program first, and the Key second, but I don't know whether that's importannt.)
7. Ignore the issue of the license number, etc. Once you've installed the "Exchange By TouchDown Key," that will verify your license for TouchDown, and give you access to the full program.
8. Curse Symantec for being such idiots, and maybe write them to say that we'd all pay 5 times what they charge, if they would get even a *little* bit better about their lack of support.
Yay! I've read other people's helpful posts in various places ffor years, and am so selfishly happy, and proud of myself, for having finally posted something meaningful myself!