There are a few reasons why your missed call auto-reply workflow may not be working.
First, if a call goes to voicemail, it will not trigger the missed call event in Workflow Builder. To enable auto-reply for calls that go to voicemail, you need to add voicemail auto-reply automation separately.
Second, for calls from a call queue, the missed event is triggered at the call queue extension, not the call queue member. To set up missed call workflows for call queue extensions, please refer to the admin guide for detailed instructions.
It's important to note that Workflow Builder’s events are currently based on the extension/user level. This means that if a call is redirected to an IVR menu and disconnected before reaching an extension, the event will not be fired for the extension's workflows. Unfortunately, the missed call event at IVR menus is not supported at this time. For now, users can create a advanced workflow for the IvrMenu extension in question using the call ended trigger and filtering by the call end reason as "CallerDropped." This will run the workflow when user ends the call before pressing any key to be redirected.