How can I get the new project name to display in the title bar of the help file?
What am I missing?
For CHM output, you change the Window properties.
You didn't say what version of RoboHelp you are using, but if it's older than 2015, the pod is named Project Setup I think. So open that pod. If it's 2015 Release or 2017 Release, the pod is named Output Setup. So open that pod, expand the Windows folder, then double-click the CHM window type you should see there.
Then change the Window Caption field.