Why can't I pull up this web page, "www.aepohio.com"..?

Why can't I pull up this web page, "www.aepohio.com"..? All of my other Bookmarked pages work fine/normal. This page is where I pay my Electric bill and with the latest Firefox update it stopped working. I can pay my bill with my phone, but I prefer to use Firefox. I checked all of these suggestions... The site could be temporarily unavailable or too busy. Try again in a few moments. If you are unable to load any pages, check your computer’s network connection. If your computer or network is protected by a firewall or proxy, make sure that Firefox is permitted to access the web. Thank You for your time, Sincerely, RandallTBrush@gmail.com