Hi @y zhang ,
Welcome to our forum!
The calendar appears all right on the pc's Outlook but just can not sync to the Outlook app on iPhone.
In order to further confirm if the calendar is synced, it's suggested that you could try to log in to you web mail to check if the calendar in the Outlook desktop client is the same as the calendar on the Outlook for web.
If so, please remove the account in Outlook on your iphone and re-add it to check if there're any differences. If the issue persists, please kindly understand that the Outlook tag here we mainly focus on general issues about Outlook desktop client. In order to better solve your problem, it's suggested to post your issue on this dedicated forum for Outlook for Mobile for more professional help.
Thanks for your understanding and support!
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