Try the following.
Start transaction SICF
Open the corresponding tree nodes for the service you would like to test i.e webgui
> default host ->sap -> bc -> gui -> sap -> its -> webgui
Select 'Test service' from context menu of the service node{enteri.e: Right Click -> Test Service
This will launch the webgui service in the browser - from here logon to system again.
It should look like the following:
https://server.port/sap/bc/gui/sap/its/webgui?sap-client=000
Regards,
Oisin