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Unable to add a server to Plesk 360 with the error: unable to verify the first certificate

Plesk 360

Symptoms

  • Unable to add a server to Plesk 360 with the error:

    PLESK_ERROR: unable to verify the first certificate

  • Online SSL checkers (such as Qualsys SSL Labs, SSL Shopper) show one of the errors below:

    CONFIG_TEXT: Intermediate certificate missing


    CONFIG_TEXT: 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.


    CONFIG_TEXT: This server's certificate chain is incomplete

Cause

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.

Resolution

*.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:
mceclip0.png

Additional Information

How to secure a Plesk hostname on port 8443 with an SSL certificate (Let's Encrypt / other certificate authorities)

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  • Good morning! My question is not about how to create a certificate for a website or any other service, that's not my query. To give you some context: I need to take an exam to get certified with Plesk University, and for that, I need to create a user account on ProctorU and take the exam. However, I need to know the name of the institution because "Plesk" no longer appears, and I need to know what name you use so I can add the institution in question and take the certification exam.

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