Web address access

I access my security cameras via a web address.  Up until 2 days ago I had no trouble access the cameras but I can no longer connect when try to connect from my desktop via an ethernet connection to my Xfinity modem.  I can connect to the web address via my ipad when I use the cellular network but cannot connect when I use WiFi.  Somehow my modem is blocking the web address.  What can I do?