Following the release yesterday of a new update for Miitomo, straight away all was not well in the Miitomo kingdom and Nintendo have since been on the case to correct the apparent issue and fix it they did.
The issue in question is of course the app crashing whenever those using iOS devices operating on 9.3 and 9.3.1, attempted to send an invite via email. Well Nintendo promised they would fix it and put out a new update and they did. Version 1.2.1 is now out and available for iOS users, but it seems there must have been some issues involved with the Android version of the app, because Nintendo also released version 1.2.2 of Miitomo for Android devices.
It is not yet clear as to what this new update does, but you can download it all the same from the Google Play store, whereas iOS users can get their new update from the App store now.