Not Understanding the WebRTC API

Looks like the problem is not relating to WebRTC API. What you heard first "This is a test call from Ring Central..." is the "water mark" of RingCentral sandbox account. You won't hear that in your production account. You also heard your own voicemail answering might be because of your extension settings which directs incoming call to your voice mailbox.

You wrote "Also, I have a RC softphone app on my Mac that is logged into that RC number but nothing happens...", I am not sure who calls whom and why both phones (mobile and Mac) should ring. Please describe better so I can understand your problem.

I have the extension set to 101 per the instructions. I tried using 1 or 0 but I get an "Invalid resource owner credentials" error. How do I get around that? I certainly don't want that happening to customers in production.

I have the softphone app on my Mac but the code is running on our server. I can get my mobile phone (the recipient) to ring but how do I ring the softphone so we're connected to the customer?

I think it is the Ring Central voicemail greeting I am hearing in the background. I can't really hear it that well because the watermark greeting is louder. If someone wants I can trigger a call to you so you can hear it.