There have been a number of problems with the latest update of Firefox 60.0.3 it revolves around the TLS security protocol that conflicts with some internet security programs that block certain websites
Not sure this is your problem but if it is editing the configuration file of Firefox should provide a temporary fix
Open a new Firefox window, type in the address bar: "about:config"
Search for "security.tls.version.max". Once found change the value from “4” to “3”
Restart Firefox.
As said this should be a temporary fix until your internet security program is updated and TLS should be returned to its default value