We have a rule set to Send Response to Sender, but the a response message is not being sent.
Rules / Incidents / Emails
To resolve this issue, there are two options:
1. Add an action above the 'send' action to: Append Response Template to Response Field
2. Disable/remove the rule. By removing the stand-alone action from the rule (or, disabling the rule), the question receipt message type will send.
The issue of the question receipt message not sending happens when the 'Send Email Response to Sender' action is used by itself in a rule. This action is not intended to be used alone and will cause the question receipt to not send as expected.
If you add the 'Append Standard Response to Response Field' action before the 'Send Response' action, this will then trigger the response message to the customer. Please note, a question receipt message will still not be sent as it is overridden by a 'Send Email Response to Sender' action.
For additional information regarding creating and sending standard response messages, please see the following published answer: