If you're on the humming power crystals page to turn in crystals from your inventory, the message tells you that the crystals get moved into your currency vault. There's supposed to be a link to the currency vault but it leads you to this dead page:

https://subeta.net/explore/vaults.php?act=currency

instead of the actual currency vault page:

https://subeta.net/explore/vaults.php?vault=currency