Just after posting this, I was finally able to update one of the fire tablets via the appstore. It's frustrating as I have twins playing together on identical devices and their updates are out of sync, last time this happened we had to uninstall one of the minecraft apps on a device to force update which meant that one of them lost the worlds that they had been working on. At least this time, they've kept their worlds. One was on v1.17.34 and the other was on v1.17.40 even though they're both set to automatically update.
Just after posting this, I was finally able to update one of the fire tablets via the appstore. It's frustrating as I have twins playing together on identical devices and their updates are out of sync, last time this happened we had to uninstall one of the minecraft apps on a device to force update which meant that one of them lost the worlds that they had been working on. At least this time, they've kept their worlds. One was on v1.17.34 and the other was on v1.17.40 even though they're both set to automatically update.