brianhpowell

Do you have any additional information? Perhaps a link to your website?
Have you tried disabling all other plugins temporarily to see if there is a conflict with something else?

I think I figured it out. My SSL certificate was only partially working. (It looked fine in the browser, but when I ran an SSL Checker, it reported some problems.) I reissued the certificate (through my hosting provider) and installed it, and Simple Lightbox started working.