Your website is secured with the SHA-1 algorithm.
The SHA-1 algorithm is now outdated and Google Chrome & other web browsers have already quit their support for it. The lower hash value and key length lets hackers crack the website easily.
Chrome 38.x users see the website as secured without any warning message, but Chrome 39, 41, 42, .... users will see this red cross error (Affirmatively Insecure).
Migrate from SHA-1 to SHA-2
You don't need to buy a new SSL certificate to troubleshoot this warning, just contact your SSL Certificate vendor or certificate authority to reissue your certificate.
Once you reissue your certificate, create a new CSR and re-install the SSL certificate on your server.
** Make sure you generate the new CSR with SHA-2 as encryption **.