I don’t necessarily want to start a new thread but in case anyone here has a similar problem, I found the simple resolution. The problem was that I first set up my Wordpress site in http. Then after buying an SSL certificate I migrated some of my site (the members section) to https.
But then my button images on the ProForms wouldn’t appear and gave me 404 errors because they were now in “https”. But since they were part of the s2member files I couldn’t change them.
After many hours searching, putting snippets in my functions.php file and installing various “SSL content secure-type” plugins, I realized the problem was that I had elected the “Hotlink Protection” in my cPanel. The protected hotlinks were all to “http”.
When I added the “https://example.com” into the Hotlink Protector, the button images and everything appeared exactly as it should!
So, anyway, rather than spending hours trying to fix 404 errors from https, all I had to do was fix the HotLink Protection in cPanel. Silly!