The first thing I would do is check to verify your system date and time on the computer is correct.
If that is the case, you can click where it says "Advanced" and then "Continue to the site anyways"
The most common reasons for that error are due to a certificate not being valid, usually either your computer's clock is wrong, or they didn't pay to renew their certificate.
Or, there is something in between your browser and their system that is causing the issue, such as a virus on your machine, but that's much less likely than your computer clock being incorrect followed by the website admin not renewing their certificate.
For more info, check here:
http://www.fixotip.com/how-to-fix-ho...google-chrome/