Comodo SSL Certificate Not Working


I bought and installed an SSL Certificate back in July for my website It’s been working fine since then, however I viewed my website this morning and got the following error from Google Chrome:

Your connection is not private
Attackers might be trying to steal your information from (for example, passwords, messages or credit cards). Learn more

I had a look at the certificates and it appears that the certificate I bought and installed is not the one being served. Is there any way this issue can be resolved?