My friend Dhalia have the same problem. Apparently the from what the lodestone said for upcoming 6.4 hot fixes maintenance:

“This maintenance will address an issue which causes servers to crash under certain conditions.
As for the issue stated in the separate news titled "Issue with Sound Not Playing Under Certain Conditions on the Windows® version", it will require approximately two weeks to be addressed. We ask for your patience and understanding.”

Hang in there pc players :3