I'm having some issues getting EWS to work with creating an appointment in Outlook, at every turn I seem to be getting the following error message (see attachment 1). This is the case when the Type is set to both exchange and to custom.
Is there something I'm missing? The formation of the appointment is all static values and not yet affected by any process values (just testing it would work first). The LFUser account has a license in 365 and I have been able to log in to O365 online to verify the password.