After connecting to the VPN, Outlook will not connect, even after entering credentials again. The bottom message on Outlook states Trying to connect.
What client VPN type are you using?
What do you see in Traffic Monitor when this connection is tried?
Is Outlook trying to connect to a private IP addr or to a public IP addr?
If a public IP addr and if the mail server is at the WG firewall location, try accessing the private IP addr.
Mobile VPN with IPSec. After chagnging Offices 365 contection to modern autenfification. VPN is not working
if you're able to hit the authentication portion of the exchange server, you should in theory be able to hit the exchange server.
If this is still happening, I'd suggest opening a support case. It'd allow the technician to gather more data about what's happening and get you to a solution more quickly.
WatchGuard Customer Support
Check the Default Gateway connection setting.
If it does not have your IKEVPN virtual IP addr, then that is likely your problem.
It is for SSLVPN connections when using modern authentication with Office 365.
Are you using the Shrew client?