Some errors in our application will be particularly common and are likely to be relatively simple to fix in most cases. This section has a quick rundown.
Note
You can find Twilio's full reference of error codes and their meanings at http://www.twilio.com/docs/errors/reference.
If Twilio has difficulties requesting TwiML from your application; for example, because your server is down, one of the error codes starting in 112 will be triggered.
These errors signify that Twilio hasn't even been able to get the TwiML from your server. Most likely, it is down, incorrectly configured, or otherwise messed up. Alternatively, the DNS records on your domain might be incorrect.
To fix this, take a look at the specifics of the error, and ideally, try placing a request yourself to see what happens.