When launching an application session, a notification is shown at the bottom right: Error: Connection reset.
A similar error is visible in awingu-application-gateway.service.log, for example:
2023-05-31 11:31:50.106376+00:00 someawingu01 awingu-application-gateway.service[java:599818]: cs-id: 9fa6508a-a0dd-443d-8034-45d286e61184 message: Connection reset
A misconfiguration on the Microsoft Windows Server RD session host.
Check if the user is allowed to log on to the RD session host.
Most commonly, it may be necessary to add this user to the "Remote Desktop Users" group.
Keep in mind that your organization may have set up more specific user groups or log-on permissions.