Hi Donghyun Ryoo Welcome to the Canvas Community.
Ordinarily I'd offer advice about it possibly being your browser. Perhaps it still is. Is the Chrome you are using up to date? Here's a guide for you to double check Which browsers does Canvas support?
If none of these methods solve the problem, contact Canvas Support. General instructions are in How do I get help with Canvas as a student? , but your school’s support setup might vary somewhat, in which case ask your local IT Department for additional troubleshooting assistance.
Sing out if you need a hand.
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