>>Modern browsers don't like SSL certs that use insecure algorithms.
>>
>>There are also reports of BitDefender being too aggressive: https://productforums.google.com/forum/#!msg/chrome/-LjiIraWUqk/ITm4JpdQAAAJ
>
>I also had to deal with a situation, once, where a certificate was not properly recognized with all browsers. The issue was simply resolved by re-issueing the certificate with another authority.

We had the same situation here that our Network Admin has been able to resolve.