Sugar Outlook plugin not opening properly

Since a couple of days, my Sugar Outlook plugin is not opening within Outlook. 

It loads but in a separate window which I cannot move nor resize instead of opening on the right-hand side of my Outlook client.

I'm running Win10, Outlook 365 and tried to upgrade to the latest 2.6.0 version of the plugin but without much luck.

It worked OK for 2 months but not now anymore and it is painful to use as such.

Any idea how to fix this?