When attempting to access GWAdmin via Chrome, Edge or Firefox a dialog is presented prompting you to 'Select a certificate'. If you click OK you will see the following:
The connection for this site is not secure
This site can't provide a secure connection
Secure Connection Failed
When presented with the option to 'Select a certificate', click the Cancel option which should then present the 'Administration GroupWise 18' login screen.
This is issue is under investigation.
The Chrome and Edge browsers allow you to reload the page and you will be prompted again to 'Select a certificate' at which point you can select 'Cancel' in order to access the GWAdmin login page. In Firefox, if you selected OK, by default this decision will be 'remembered' and you will continue to see the 'Secure Connection Failed' message on subsequent attempts to access GWAdmin. To resolve this in Firefox, while still showing the 'Secure Connection Failed', click on the 'circle i' to the left of the URL and choose the option to 'Clear cookies and site data...' and select Remove when prompted. Reload the page, verify 'Remember this decision' is checked and select 'Cancel'.