Got UC500 & 520 switch. Have created Hunt Groups and added members but get Busy when I dial HGPN. I also intermittently get Busy when dialling a DN which is free??
The thing is that a second call to the same shared DN will go only to the ephone that took the first one.
The workaround is to configure a chain of DNs large enough to accommodate the number of calls that you anticipate can be received, and place said DNs in overlay on a single button with the "c" keyword.
All that is confusing enough so in CME 4.3 Cisco introduced parallel hunt-groups, octo-line DNs and removed the stickiness of subsequent calls to the engaged ephone.