SSL Certificate trouble

I have a free SSL certificate from Cloudflare. Since the recent changes Google made, I'm having trouble with it. I have the certificate and the private key installed on the server, but when I check my domain, I get an error "no certificate subject alternative name matches Unable to locally verify the issuer's authority"

Is this because the certificate is free? is there something more that I need to do because of the changes? or do I need to purchase a certificate now? :fearful: (Pinching pennies, setting up a nonprofit...) I'd appreciate any insight. Thanks.