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ChenguangHe - Glad to hear that your issue is resolved.
For AADSTS65005: The application asked for scope OnlineMeetings.ReadWrite.All that doesn't exist on the resource issue, 

Go to the app registration blade in Azure AD find the corresponding app registration whose App ID is mentioned in the error. Once you find the app, go to its API Permissions section and based on the type of token you require like delegated permission (if you want to access token in user's context) and application permission (if you want the access-token in application's context) check if OnlineMeetings.ReadWrite.All permissions is listed there or not.
 Also please refer this thread which is in similar line and check if it helps.

Thanks, 

Prasad Das

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