I have solved the problem. Even though it is not the answer I expected, I post this answer just in case it is helpful to the rest of the community.
I created a new project and copied the cpp/h files from the non-working project into the new project. The new project compiles. With the new project I can now add other private variables to the class and access them in the constructor (as well as the IDE). All parameters I have easy access to show the projects to be identical, yet one compiles and the other does not. I can only conclude the project itself somehow became corrupted (which does not inspire confidence).
While I am relieved it was not a stupid programmatic mistake on my part, I am disappointed in not being able to find and fix whatever was wrong with the project files. Thanks to all those who offered suggestions.