Two way sync with Office 365
Under WP Admin > BookingRobin > Providers > provider detail page > Calendar Sync section, check Enable calendar sync.
Click grant authorization,
Click Office365, input your account email address and password to sign in.
Click Accept to give permissions to access your personal calendar.
and then copy the generated code to Authorization Code field, and click update.
Once it is added, you are able to choose your personal calendar to sync with. Do not forget to click save before leaving the page.