Gonna say didnt even have to read the whole thing to see thats the same that happened here. Not that I'm claiming everyones issue is the same. But basically what happens is:
1. Have X amount of ncoins in your account.
2. Purchase some keys/items -> these transactions happen normaly and fine
3. Purchase more keys/items -> THIS transaction fails/bugs out. Either receiving an ingame error message like "transaction could not be completed do to system errors" or simply not receiving the items at all without any message.
4. The FAILED transaction does NOT show up in the ingame purchase logs or on the website. Neither do GMS seem to be able to locate the failed transaction attempts.
5. Your account balance is not imediately updated visually, however internally it seems like the system already deducted your ncoin for the "failed/error" purchase.
6. Couple of hours/day later your account balance updates and you lose X amount of ncoins from the failed purchase without receiving any items. @Cyan@PhoenixMitra can you please relay this info to someone? Support hasnt responded in 2-3 days for most people and they seem to be having issues since then cant locate the failed purchases in game since it doesnt show the logs. Most people didnt bother to take screenshots or anything, but I myself provided them with all the account recharge info and screenshots of the error and then the account balance once the Ncoin vanished from it and the ingame purchase tab etc.