[GTALUG] 'Unable to connect' to https://www.mixingmusiclive.com/

Hi, Firefox suddenly can't load anything at https://www.mixingmusiclive.com/ I don't have a firewall - no that I know of. Searching on Internet for things to try, but as usual hitting problems like advice is to hit Alt, then Tools, then Options, and, of course there is no Options. I have checked with the web admin and she says everything is good at her end. Ideas? Chris