Unable to add a server to Plesk 360 with the error:
unable to verify the first certificate
Online SSL checkers (such as thawte CryptoReport, Qualsys SSL Labs, SSL Shopper) show one of the errors below:
Intermediate certificate missing
The certificate is not trusted in all web browsers. You may need to install an Intermediate/chain certificate to link it to a trusted root certificate.
This server's certificate chain is incomplete
The certificate consists of 3 parts:
- *.key file private key;
- *.crt - certificate itself;
- *-ca.crt - certificate of Certificate Authority.
The error means the Certificate Authority (ca.crt) part of the certificate is missing.
*.key / *.crt / *-ca.crt parts of the certificate should be provided by the corresponding Certificate Authority.
Contact the certificate issuer and ask to provide CA part of the certificate:
Rename the existing certificate under Plesk > Tools & Settings > SSL/TLS Certificates > certificate _name > Rename.
Then, install the certificate again. All three parts should be uploaded/filled for the certificate:
How to secure a Plesk hostname on port 8443 with an SSL certificate (Let's Encrypt / other certificate authorities)