Same exact issue as OP on two iPads. The problem started after updating to 1.2.13 yesterday. Coin balance is now zero, all in-app-purchases are gone. Updating to 1.2.14 did not correct the problem. I have a third iPad which was not updated to 1.2.13, and still works fine. I noticed when accessing the Minecraft store, the one running 1.2.11 says "Disconnected!" at the top, and the two that are affected say "Sign In". I believe the issue is pertaining to Xbox live.
Same exact issue as OP on two iPads. The problem started after updating to 1.2.13 yesterday. Coin balance is now zero, all in-app-purchases are gone. Updating to 1.2.14 did not correct the problem. I have a third iPad which was not updated to 1.2.13, and still works fine. I noticed when accessing the Minecraft store, the one running 1.2.11 says "Disconnected!" at the top, and the two that are affected say "Sign In". I believe the issue is pertaining to Xbox live.
2017 iPad
iOS 11.3 (latest)
Minecraft 1.2.14