How to access form properties in Mail task?

I’m working on my first process with Flowable UI apps. I created a user task with a form to collect a couple details from the user, followed by a Mail task to send an email to someone. In the Mail task property Text, I put some static text and a couple references, ${name} and ${message}, to properties from the form. Running the process generates the following error in the Tomcat log:

11:38:30,816 [http-bio-8080-exec-8] ERROR - Unhandled exception org.flowable.engine.common.api.FlowableException: Unknown property used in expression: Simple, plain text message. Nothing much to see here.
From = ${from}
Message = ${message}
at org.flowable.engine.common.impl.el.JuelExpression.getValue(

What am I doing wrong?

Can you paste the xml of the mail task?
Did you verify the ids of the form properties are exactly the same as used in the expression?

Joram, thanks for asking the questions. I thought the IDs in the email body matched the form property IDs, but one reference was wrong. I corrected the bad ID and now all is well!