From the beginning of december 2015 Twilio will only work via HTTPS.
You will need to replace the integration code of your call buttons with new integration code, which explicitly adds 'https' before url of 'track.js' file. (old integration code uses so called 'protocol relative url' starting with two forward slashes '//')
URLs for Twilio numbers / Twiml apps in Twilio account can remain with http if there is a redirect or if you have also http enabled.
Twilio only accepts (trusts) certificates on this list approved by Mozilla. If your server certificate is not signed directly by one of the listed root certificates (i.e. if there is an intermediate certificate used), you will need to use format called "certificate bundle", where instead of using just your server's SSL certificate, you can enter whole certificate chain. You can create a certificate bundle file by concatenating the server's SSL certificate followed by intermediate certificates (signing certificate must follow after signed certificate). The certificate bundle can then be used in server configuration of your own server, or in the Configuration > General > Domain settings section in certificate field.
Otherwise you may receive response with HTTP code 502 with Twilio error 11237 and error message: Certificate exception:PKIX path building failed sun.security.provider.certpath.SunCertPathBuilderException: unable to get valid certification path to requested target.
HTTPS is automatically enabled for accounts hosted at ladesk.com.
If you are using a custom domain with an account hosted at ladesk.com and you want to be able to use Twilio, you absolutely have to have an SSL certificate. Please follow our domain parking guide section about custom SSL certificate.
Agents must log into LiveAgent agent panel via URL with https.
If you are using a downloadable version of LiveAgent installed on your own server and you want to be able to use Twilio, you also have to have an SSL certificate.
Agents must log into LiveAgent agent panel via URL with https. To be sure your agents use the correct way of logging in, it is best to add a redirect from http to https.