Shared mailbox

Hi

I'm connecting to a shared mailbox. Works fine in desktop when I select UPN. Data refreshes fine.

Now, in the service portal I must configure credentials, and choose either basic/oath2 options. I tried both, using same account as in desktop, both returns a status 400 and "We were unable to use the provided Exchange credential to connect". 

Any clues on what to try would be hugely appreciated

Thanks