Can't get a connector to authorize - now what?

I've been struggling to authorize a connection to the Microsoft PowerBI connector since April. 

Our IT team has indicated they have done everything on their side to extend the rights, access, permission etc. 

In reaching out to Fusion support, they were helpful in offering some documentation as to what it might be but indicated it is the extent of their support. 

I'm not sure where the miss is - MS SharePoint and MS Outlook connectors work fine. 

Does anyone have any suggestions on ideas it might be? Thanks!

Christina