Device info page won't open

My Xfinity device info page:  https://www.xfinity.com/support/devices  will not load. It used to open, but since I got a new modem a few days ago, I cannot access that page in my account. The other Xfinity pages in my account open fine. I'm using Firefox. I also tried with Microsoft Edge, but that didn't work either. It used to open fine with Firefox until I got the new modem. Now the page won't load. I tried the Xfinity customer support chat but they didn't help at all. They used their usual trick of "It'll be fixed in an hour. Try again then." Any help would be appreciated.