When using Switchboard Pro, the user is talking to one person on an extension, when a second and then a third call come in to the same extension. The second call continues to ring until the user can answer it, but the third call goes immediately to the extension's voicemail without giving the user a chance to answer it.
A quick, simple, and powerful fix for this issue is to order the Power Keys 6 (PWR 6) add-on for any VVX extension, which provides support for six simultaneous calls. If the VVX extension has a sidecar, you can order Power Keys 28 (PWR 28), which provides 10 additional simultaneous calls, for a total of 12 simultaneous calls. If both PWR 6 and PWR 28 are ordered on an extension, the extension would be able to handle a grand total of 16 simultaneous calls support. Explore the features of Power Keys here and contact your Sales rep to order.
Switchboard Pro inherits the extension’s simultaneous call capacity when it is assigned to the user. It is set to two by default.