When using the Portal interface in a browser, select Monitor -> Virtual Service Environments -> VSE and display a list of virtual services.
Then when filtering on a group tag name with a hyphen or dash, the virtual service with that group tag is not selected.
This issue is caused by a defect.
The workaround is to use group tags without hyphens or dashes.
A patch can be requested by logging a case on support.ca.com by referring to defect DE356757.