If users utilize the same extension for taking calls, then one will not be able to get calls if the other remains logged in. This usually occurs when users work in shifts, and multiple shifts involve using the same extension. Should a previous shift worker not log out of the extension on their softphone, then the next worker will not be able to use the extension and calls will route to voicemail.
Have the previous user log out of the extension on their softphone. Then calls should route to the current worker’s softphone via the same extension.