Dear Toby,
Thank you for providing us the additional information. I can confirm that the same defect was also raised previously by other users as well as our internal test team and was added on a high priority list for the next release of Vienna which is due to be released on 9th July.
In the current version, you can either leave the URL field blank or temporarily add IP Address instead of the server name for example:
http://192.168.1.5:90/test/
instead of
http://my-server:90/test/
Any other questions, please do use our forums.
Kind Regards,
NMQA Support