Solve the problem of accessing 12306 "untrusted connection" in Firefox

When I access 12306.cnvia Firefox, the message "this connection is untrusted" is always displayed. There was a "add exception" button, and now there is no more. Only "Get me out of here! ". So," What should I do? "

"What shoshould I do? "Escaping will never solve the problem. Find it and solve it:

Option-> advanced-> encryption-> View Certificate-> server-> Add exception-> location: https://dynamic.12306.cn-> Get Certificate-> confirm to add. close Firefox, open it again, access 12306, okay!