Thanks for the question @dwhitworth1. We don’t do any checks in regards to SSL within the plugin. We check for requests to /ads.txt or /app-ads.txt and output the proper content in either scenario. But we don’t do anything in regards to whether it loads over http or https, that should just default to whatever settings you have set on the server or WordPress level.
The way this plugin works is similar to how WordPress itself handles the default /robots.txt file. Looking at the site URL you provided, I can access that file (/robots.txt) over both https and http, the same as the /ads.txt file. I can also access the default /feed URLs over both as well. I know you mention that you have SSL forced through WPEngine settings, but I’d reach out to them to ensure all URLs are truly forced over SSL, as it seems at the moment that certain URLs aren’t, like /robots.txt, /feed and /ads.txt.
