The flowrepository.org certification will expire shortly or already has. As of January 15th at 2:00PM PST (5:00 PM EST), we are waiting on InCommon to do some delegation to allow for the new certification to be issued. It's very likely that this will not happen before the certification expires.
There is a security concern with not having a valid certification. You will have to click through a browser warning and connect to the site. While traffic will still be encrypted, this does make it much easier for someone to perform a man-in-the-middle attack and snoop traffic, including typed passwords. If this is at all a concern for you, please refrain from logging in until this warning message is removed and hence the certification is restored.
Sorry for any inconvenience.