If you've created a Process Builder that fires on a Task and uses a Messaging Template, and that Messaging Template contains Merge Fields, those Merge Field will not update with the corresponding values. It sends the Message to the Messaging User's device from the Account or Contact, but won't pull in the merge fields as you may expect.
The error received in the Messaging Error Log is:
"Can't insert the merge fields into the message because Quick Text isn't supported on the object you specified in the process. Messaging sends the message without the merge fields. Re-create the process using an object that supports Quick Text. Or re-write the message without the merge fields."
Task is a standard object that has a child relationship to both Account and Contacts.
This is expected behavior. The Task object does not support Quick Text (which powers Messaging Templates with merge fields), because sending an Activity from another Activity is not supported in Salesforce. To use merge fields in an outbound Messaging Template, the trigger object must support Activities. Below is the recommended workaround:
In order for this to work, the object you're sending from must support Activities, and sending an Activity from an Activity (Task in this case) is not possible.
Use a custom object or a standard object that supports Activities and use that as the context to map the same information from the Task to the chosen object. Then create a Process Builder that triggers an outbound message when the chosen object has a new record created.
000388994

We use three kinds of cookies on our websites: required, functional, and advertising. You can choose whether functional and advertising cookies apply. Click on the different cookie categories to find out more about each category and to change the default settings.
Privacy Statement
Required cookies are necessary for basic website functionality. Some examples include: session cookies needed to transmit the website, authentication cookies, and security cookies.
Functional cookies enhance functions, performance, and services on the website. Some examples include: cookies used to analyze site traffic, cookies used for market research, and cookies used to display advertising that is not directed to a particular individual.
Advertising cookies track activity across websites in order to understand a viewer’s interests, and direct them specific marketing. Some examples include: cookies used for remarketing, or interest-based advertising.