We are also experiencing the same issue after "upgrade" to 1.2.15 on an iPad Mini: coin went to zero and skins locked. Initially, it was just a couple of skin packs, but Xbox customer support advised us to delete and reinstall the app. After that, all purchases are locked.The Restore Purchases button and buying the free pack does nothing.
Trying to resolve this issue on the advice of Xbox Support resulted in a complete loss of all my son's data. Do NOT contact them or believe what they tell you.
I searched the Mojang support site for "coins disappeared" and got this page: https://help.mojang.com/customer/portal/articles/2815078
It says:
"I bought coins but they are not showing up on my account. What do I do?
If the purchase is visible on your account when you log in to your account at account.microsoft.com, try restarting your device. Make sure that you are logged in to the same account that made the purchase. If you are still unable to see the coins you have purchased, contact Xbox Support."
I followed this advice and contacted Xbox Support. The technical support agent there told me to delete and reinstall the Minecraft app and that would resolve the issue. I asked if that would result in any data loss. He assured me it would not. I went to delete the app and saw the iOS warning that deleting it would delete all of its data. I asked again if deleting the app could cause loss of data, and the representative very confidently stated again there was no chance of losing anything.
So, I deleted the app, and now after chatting with another XBox rep for an hour and researching online, it appears that all of the worlds that my sons have spent hundreds of hours building on the device are gone. (iCloud backup was not enabled on the device.) He is devastated.
It is bad customer service for Mojang to refer it customers to the parent company's support if that service does not have enough knowledge to offer good advice. It is shameless negligence to do so when XBox support provides incorrect instructions about issues that could lead to devastating data loss assertively and without equivocation.