Using Hybrid Exchange (CRM On-Premise 1612 v9.0.3.7 - Exchange Online) server side sync, App deployed to users, all mailbox tested / approved / successful. same with server test.
Trying to launch the app in Outlook for the users gets stuck on "We're just getting things ready" The same happens if the mailbox is opened via web OWA.
Network traffic log displays repeated tunnelling to crminsights.crm.dynamics.com:443 nocache-must revalidate.
I have tried clearing browser cache in Edge, IE, Chrome, and added the below to trusted site.
*.dynamics.com
*.microsoftonline.com
https://login.windows.net
Can anyone offer any advice?