SSL Certificate Not working with GTMETRIX or Giving Error on “err_cert_authority_invalid” on mobile chrome only

SSL cert “err_cert_authority_invalid” on mobile chrome only

Using CentOs you may see this error in your android chrome browser or you may try analyzing your website on gtmetrix
and gtmetrix may reject your site analyzing process due to incorrectly installed SSL.

Problem: you are missing Intermediate Certificate.

This solution is for POSITIVESSL - COMODO SSL:

1) Open Zip file you received with certificate.

- AddTrustExternalCARoot.crt
- COMODORSAAddTrustCA.crt
- COMODORSADomainValidationSecureServerCA.crt
- domain.com.crt

2) Now create one CA.TXT file and open in any text editor. 

Now also open 
- AddTrustExternalCARoot.crt
- COMODORSAAddTrustCA.crt
- COMODORSADomainValidationSecureServerCA.crt
- domain.com.crt
in any text edito and copy those certificate information to CA.TXT one by one and upload ca.txt on your server

may be here /etc/pki/tls/certs

3) Httpd-vhosts.conf

SSLEngine on
SSLProtocol -ALL +SSLv3 +TLSv1
SSLCipherSuite ALL:!ADH:RC4+RSA:+HIGH:+MEDIUM:!LOW:!SSLv2:!EXPORT
SSLCertificateFile /etc/pki/tls/certs/domain.com.crt
SSLCertificateKeyFile /etc/pki/tls/certs/domain.com.key
SSLCACertificateFile /etc/pki/tls/certs/ca.txt

Now test and your problem would have been solved