Syncing a Fitbit Ace 2 with a Fire Kids Edition Tablet

Things to know before you get started:

1. Fire Kids Edition tablets are not officially compatible with Fitbit trackers.  If you desire a device that makes syncing a cinch, pick one from this list.  FOLLOW THESE INSTRUCTIONS AT YOUR OWN RISK.  You can get your child's Ace 2 to sync with the Fire Kids Edition tablet, but it involves changing settings that lower the security and stability posture of your device.
2. These instructions are for the Fire 7 Kids Edition Tablet, 7th Generation.  At the time these instructions were written, it was running Fire OS 5.6.4.0 (636559920), which according to Wikipedia is the latest version for Fire HD 8 and Fire HD 10 (7th Edition) and is analogous to Android 5.1.1 Lollipop.
3. There is a Fitbit app available in the Appstore, but it is not compatible with Fitbit Family Accounts.  At the time these instructions were written, the version of the Fitbit app available in the Appstore is 2.63, but the first version with Family Account is 2.72.  The latest version of the Fitbit app that works with Android 5 is 3.4.1, and I don't expect there will be any more updates compatible with this version of Android.
4. Technology changes rapidly, and there is no guarantee how long this method will continue to work.
5. You (the parent) will need your own Fitbit account in order to create a Family Account.  You can create a profile for each of your children under the Family account.  If your child is 13 or over then they can create their own account, but a child that age or older probably doesn’t want an Ace 2, which is targeted to ages 6+.  Fitbit has an extensive and helpful FAQ for setting up Fitbit Ace devices.
6. These instructions assume you have some familiarity with the Fire Kids Tablet and can navigate between users (parent and child).

How to sync a Fitbit Ace 2 with a Fire Kids Edition Tablet

1. Sign into the Fire Kids Edition Tablet with the parent's account.  You will need access to many system settings and features that are not available when signed in as a child in the Freetime mode.
2. Go to Settings > Security & Privacy.  Under Advanced, enable Apps from Unknown Sources.  It will give you a warning.  Make sure to read it and decide if installing the Fitbit app is worth the risk.  This is your "Matrix moment" to take the "blue pill" and keep this setting disabled, or take the "red pill" and try to get this to work.  I felt like the risk was low since Fitbit is a well regarded technology company.  The more apps you install this way, the more risk you introduce with your device, so follow this method with caution.  As your tablet warns you, "you are solely responsible for any damage to your Fire or loss of data that may result."  Tap OK to continue.
3. Using the Silk web browser, download the APK for the Fitbit app.  This is a method of app installation known as "Sideloading."  APKMirror is regarded as a reliable site for downloading older versions of Android apps, but again, download and use at your own risk.
4. Open the APK file.  You can Open from the Silk browser once it completes, or you can use the Docs app and go to the Download folder.  It has a super long file name: com.fitbit.FitbitMobile_3.4.1-20213430_minAPI21(arm64-v8a,armeabi-v7a,x86,x86_64)(nodpi)_apkmirror.com.apk.  Again, you will want to read over the Privacy and Device Access warnings and decide for yourself if it is worth the risk.  Then tap INSTALL.  This install feels like it takes forever, but hang in there.  It should complete after about 3 full minutes.
5. Tap on OPEN to make sure that it was installed correctly.  You will want your child to be able to sync with their own profile, so don’t login, just close the app.
6. If you have an SD card to expand storage, make sure to "Move to Tablet."  Our tablet has an SD card so that we can store more music, videos, and apps without taking up storage on the device.  However, we found that both Minecraft and Fitbit need to be stored on the device Storage in order to work properly.  This may be a limitation for any apps that are shared by a Parent account to a child's account.  To do this, go to Settings > Apps & Games > Manage All Applications, and tap on Fitbit and tap on "Move to Tablet."
7. Share the Fitbit app with your child's profile.  Go to Settings > Profiles & Family Library.  Choose your child’s profile and tap on Add Content.  Tap on Share Content, tap on Games, select Fitbit and tap DONE.  You are now ready to test the app using your child’s profile.
8. Switch to your child’s profile and "download" the app.  The Fitbit app should appear in the list Added For You.  When they click on it, it will take a minute to download to their profile.
9. Once the app is successfully downloaded and you can open it, you will need to sign in with the Parent account.  Then under Account choose My Family and select your child’s profile by clicking on Switch to Kids View.
10. Once in Kids View, click on your child’s profile icon and tap “Set up a Device”.  You will need Bluetooth turned on to complete this process, and the app will walk you through the steps.

Troubleshooting

This process took me several hours to figure out, and I ran into a lot of issues along the way.  I wrote this article to save you some time, and hopefully you can learn from some of my mistakes.  Here are a few issues and how I resolved them:

• "App not installed."  I downloaded the APK to the tablet, was able to open it and start the install process, but it gave me the message "App not installed." - such a helpful message!  I downloaded several APKs and tried installing different versions of the app, but none of them worked.  Thinking there might be an issue with the install files from APKMirror, I sideloaded the Google Play store to try and install the app (it chose 3.4.1 for my device).  When I did so, it shared a more helpful message that an incompatible version of the app was already installed.  Then I remembered that I had installed the Fitbit app from the Appstore.  While I had uninstalled the app  (Settings > Apps & Games > Manage All Applications, tap on Fitbit, tap the Uninstall button), apparently it was not fully uninstalled.  I clicked on the 3 dots to "Uninstall for all users," and after removing the app from all profiles, I was finally able to install a newer version of the Fitbit app successfully.
• “There was an error: Please try again or contact Amazon Customer Service.”  I got to the point when the Fitbit app was showing up under my child's profile, but the Download was not succeeding.  The app icon showed an exclamation point.  When I long-clicked and chose show Show Error, it said “There was an error: Please try again or contact Amazon Customer Service.”  Since this is a sideloaded app, Amazon Customer Service will not be able to help you.  What fixed this issue for me was moving the app from the SD card to the Tablet, outlined in Step 6 above.
• "Unable to locate device."  The app was installed, I logged in and chose my child's Fitbit profile, but the Ace 2 would not sync with the tablet.  I was concerned that there was a Bluetooth incompatibility between the tablet and the Ace 2, but what turned out to be the issue was that I had already been syncing my child's tracker to my phone, and it can only sync with one device at a time.  To resolve this, I synced the Ace 2 with my phone one last time to save all of their data, and then I removed the Ace 2 from their profile (in the Fitbit app, tap on the child's icon, tap on the Ace 2 tile, and scroll down to the bottom and tap on "Remove This Ace 2").  I then opened the app on the tablet and set up the device (steps 9 & 10 above).  The tablet found the device, I was able to enter the code, and there was much rejoicing!