Greetings,

Currently, there's an error occuring in in-game shop called ("unknow error2") where you cannot use items.
This is occuring due to delayed data transmission.
However, the shop can be used normally if you wait around 5 minues after opening the in-game shop.
We are working diligently to resolve this issue as soon as possible.
We deeply apologize for any inconvenience this has caused.

Thanks for your understanding.

MU support team