when having truble reaching the board, seems it's usually dns poisoning of some kind. secure dns helps, and when that fails, changing secure dns providers usually fixes.
wrt firefox and problems reaching site: a few updates back, firefox changed the dns-via-https settings such that they want a name and not an ip address, thwarting use of 9.9.9.9 tha previously worked. https://dns.quad9.net/dns-query is currently working but seems like by using a name and not an ip they can interfere.