I think you also asked this question to our support email ? You will receive an answer to that as soon as the issue is fixed, most probably tomorrow. We do not sell addons through appstores because license agreements require these to be personalised. 

You should have been able to buy this FLARM license without any problem, but I suspect there is a shop attribute set to this item to avoid people without an active subscription buying this. We had "problems" in the past where users bought an addon product, no realising it only works with an existing EasyVFR license. This check however does not work for users who bought their license through Apple appstore, and should simply be removed. I asked the shop maintainer to do this asap. 

Sorry for the inconvenience causing!

ALL fixed Now Thanks to Tims rapid work o the Shop Maintenance front....!