Turns out the problem is that the WA_Universal_Email folder is not in the root of the site, rather it was in the same folder as the page calling it. It was originally created in an empty site and then moved into a folder along with all relevant files, just as it appears - AND WORKS - on the server.
Why are all of the WA supporting files automatically created in the site root? It makes for a rather messy folder structure at times. I would prefer to keep these folders where I want them.