As developers who want as many people as possible to play Terraria, we will never intentionally make devices incompatible by choice.
Occasionally there will be a necessity for us to do upgrades to stay in line with the requirements given to us by Google/Amazon/Apple stores, this can mean that some older devices will become incompatible.
If your device was previously compatible, but now all of a sudden isn’t, please double check your device against the requirements here: https://support.505games.com/hc/en-us/articles/360014954000-What-are-the-minimum-system-specifications-and-requirements-to-run-Terraria-on-my-mobile-device-
If it should be compatible, please ensure that your device has not been rooted, or changed outside of the manufacturer’s suggestions. This can cause stores to detect your device/account as untrustworthy and prevent you from downloading legitimately owned products.
If you are still unable to get the latest version, then please post on the Terraria Community Forums for assistance. (https://forums.terraria.org/)