On my TwiML app, when I click the call button, the seconds start to count but nothing happens. I don't receive the request on my server, and I'm sure the url is correct.
Previously if something didn't work, I heard Sorry, an application error has occurred, but now I get nothing.
Twilio evangelist here.
I'd suggest using the error callback function to see if the library is reporting a specific error back to you.
I believe we also output those error codes to the browser console as well, so I'd also suggest checking there.
Hope that helps.