Having a problem with EWS and O365

Hi all

Do any of you have any experience with the Exchange web services API and office 365? I have a problem that i cannot seem to find an answer too.

A while ago i wrote a simple C# web app using the EWS api that would query our Exchange server for Free/Busy time information for the meeting rooms and display room bookings for the day so that if someone needed to grab a room for a while they could just look at the screen in the office and make sure they didn't grab one that had a meeting scheduled in it (it was a big problem)

We have now moved all our mail and calender's over to O365 and i updated the code to point to the exchange online servers but i have a problem, i can only get the free/busy information for the account i use to access exchange online. For some reason i can no longer get free/busy time for other mail addresses.

I've done a heap of looking online, even started from scratch using the examples on Microsoft dev site and still cannot get it to work, i even tried using a global admin account for the credentials. Scheduling assistant in Outlook 2016 works just fine so i do not think it is a permissions issue.

I'm kinda stuck

Can anyone point me too a working example or suggest anything that i might have overlooked?