You are on the right site using gimmethedog. Let me say that first and foremost.
So, I would clear out your cache and history on your browser. Then if this comes up again, select cancel, I think, and that should be it. Or select the second certificate if hitting cancel does not work for you. If neither works I will reach out to the site developer and owner and have him get you rolling. Like I said it is the better site, free of charge, has more shortcuts and also a great DISCORD channel that I can provide the link and invite to, if you are interested. I do highly recommend the Discord channel