Thanks for your help with this.
I have logged out & even rebooted the server in between login attempts but receive the same error.
The Veeam Reporter service is running. I had an issue during installation with the service failing to start and had to extend the service start timeout value as in this article:http://www.v-strange.de/index.php/veeam ... ss-service
That resolved the service issue and it has started successfully on subsequent server reboots.
The service is running with an AD service account I have created. This account is also a member of local administrators and Veeam ONE Administrators groups.