When you receive an incoming call while logged into the branded portal or dashboard, you will receive a popout with options to Reject or Accept the call.
When you have an incoming call, and you press the accept button; the PBX will cancel the current SIP INVITE to your phone and send a new INVITE with a Ring-Answer Alert header. The Ring-Answer tells your phone to answer the call automatically.
When you press the Reject button, the INVITE(s) sent to your phones will be canceled, and the caller will be sent to the 'Forward No Answer' Destination defined in the answering rules.
Why is my Accept button 'grayed' out when I receive an incoming call?
The PBX needs to be clear on which device will answer the call. Therefore, the accept button will only work when you have a single ringing destination associated with the user. If you ring multiple devices under the same user, the button will be disabled ('grayed' out).