Why can't I access github.com after updating to the latest version of Firefox? Adding an exception still doesn't allow me to establish a connection.

[yangqi]

狐狸看向警告标志的插图。 当心，似乎有异常情况。 Firefox 发现 github.com 存在严重的安全隐患。若有人冒充此网站，其可试图窃取您的信用卡信息、密码、邮箱地址等信息。 github.com 启用了被称为 HTTP 严格传输安全（HSTS）的安全策略，Firefox 只能与其建立安全连接。您无法为此网站添加例外，以访问此网站。

[SuziH]

I have battled to access a number of sites after the latest update. They are not recognizing my IP so I have had to go through hoops to get back to normal. What went wrong Mozilla?