Cannot send email and connect to calendar in Microsoft graph

When trying out graph explorer (https://developer.microsoft.com/en-us/graph/graph-explorer) to execute office 365 APIs using my company account, I am encountering an error below when using APIs for Outlook Mail and Calendar. Same error encountered for the applications that I have downloaded in Github. Applications that are trying to access the calendar APIs. I have also tried to create a developer account for office 365 and it has the same error message when accessing the APIs.

 

Error response: { "error": { "code": "ResourceNotFound", "message": "Resource could not be discovered.", "innerError": { "request-id": "351f57d5-3bdb-4c6f-a06c-b204f23d0eda", "date": "2018-06-13T03:12:28" } } }

 

But I can access User APIs. Like getting my profile details in the Company AD. Successful response: { "@odata.context": "https://graph.microsoft.com/v1.0/$metadata#users/$entity", "id": "987f2dcf-a66c-4f14-a180-41e2eac0b65c", "businessPhones": [ "+47 37 50 46 15" ], "displayName": "Teemee F Tang", "givenName": "Teemee F", "jobTitle": null, "mail": "[email protected]", "mobilePhone": "+63 947 33 71109", "officeLocation": null, "preferredLanguage": null, "surname": "Tang", "userPrincipalName": "[email protected]" }