Quick Reply buttons are being sent by bots and users have confirmed the issue is resolved.

Facebook has released a fix for this issue and is saying quick reply buttons should work from now on. We are monitoring the situation.
Please see this thread for more information: https://developers.facebook.com/status/issues/420902649044839/

Facebook has provided an update that there is a fix ready to be implemented and will provide another update when it is ready:
https://developers.facebook.com/status/issues/420902649044839/

Facebook says all Quick Reply buttons will send after the fix has been implemented.

Facebook has said there is a partial outage and they are investigating. You can follow this thread for more information.
https://developers.facebook.com/support/bugs/191892809272888/

Starting to see a few more reports of the issue with 'Quick Reply' buttons not showing from other providers and messenger developers. 'Quick Reply' buttons are not displaying on desktop, iOS, and Android devices. We are still investigating and will provide another update as soon as possible.

There are reports that Quick Reply buttons are not appearing in messenger. We are investigating the issue and will provide updates as soon as we have them.