CiviCRM: WordPress V5.6.2, hosted on CiviHosting
We can successfully send outbound SMS messages but cannot receive replies back through the webhook in Twilio. We either get HTTP 404 Not Found, 502 Bad Gateway (both encountered on version 5.X), or Schema Validation required responses (encountered on version 4.7).
We followed the CiviCRM setup documentation here, including using the example callback URL.
I have noticed other posts on Stack Exchange highlighting similar issues with different suggestions for callback URLs but all of those different URL configurations have failed, and none of the posts seem to define a clear answer/solution.