App has stopped showing instant transaction notifications?

As far as I’m aware, this feature hasn’t been changed - you should still be receiving notifications for every purchase. That’s assuming that you haven’t changed this setting either -

So I’m afraid the usual advice, force quit & reopen the app, then if that doesn’t work, delete the app & reinstall it, is probably your best bet here.

There have been notifications bugs in the past so if none of the above works, please do let us know.