We have two Kindle Fire Devices that cannot connect to realms. On the Worlds tab, there is a message that says "All Reams have been updated. You need to update your game to continue playing Realms."
I do not have this problem with Minecraft on Win 10. I can enter the realm fine.
One difference that I notice is that on the Kindle, the version listed on the splash page is v1.14.21, whereas on Win 10 it is v1.14.20. The Kindle app was updated on 1/30/2020, whereas Win 10 was updated on 1/28/2020.
I am having the same issue. I updated to the latest hotfix and now can't join any realms. Tell me "All Realms have been updated. You need to update your game to continue playing Realms." I am on version 1.14.21 which is the latest version of the game. I have tried force stopping the app and clearing the cache with no success. I have also tried hard resetting my kindle several times with no success. I have the Kindle Fire HD 8 6th Gen.