I applied the font from the latest beta version, but there was an error that could not be displayed. It works well on the PC, so please check if it’s a personal error.
Since you are Korean, there may be an error in translation. Please excuse me.
I can’t see any problems with your CSS. If you are still having trouble, it may be worth trying a different font like Arial - if that works, the issue may be the specific font you’re using.
Also, please note that the font you are trying to use appears to come with iOS, so you should not need to include the .ttf file: