Well that’s a big deal.
If you are running a Symantec certificate issued before June 1, 2016, and you do not replace the certificate, come April 17th, your site will be regarded as unsafe. The browser will display a big nasty warning that “Your connection is not secure” and most would-be visitors will be long gone.
Failure to replace your certificates will result in site breakage in upcoming versions of major browsers, including Chrome.
If you want to test your site https://www.google.com/chrome/browser/canary.html