Just checking the wording, What window do you expect Firefox to open or do you mean you can't open a window to see firefox. I'm thinking you can open firefox but see nothing in the window, i.e. your server. It seems that lately there was a security update relating to connecting to local servers, I will see if I can find it. However I have no difficulty accessing my home server, locally or remotely via Fx 150.0.3 ''' UPDATE:''' https://support.mozilla.org/en-US/kb/control-personal-device-local-network-permissions-firefox