NetScaler SSL Certificates missing after upgrading Secondary Node

1. Reinstall the missing certificate.

• Reference document: https://support.citrix.com/article/CTX461396/certificate-binding-lost-after-upgrade

• Do not manually modify files in the /nsconfig/ssl/ folder or use API calls to do so, especially on the Primary node.
• Do not perform certificate file installation, updating, or deletion on the Secondary node. All modifications should be made on the Primary node.
• Do not upload certificate files that have identical content to any existing certificates installed on the NetScaler.
• Do not upload or update certificate files that have the same filenames as existing certificates on the disk.

Problem Cause

• Manually modifying files in the /nsconfig/ssl/ folder or using API calls especially on the Primary node.
• Performing certificate file installation, updating, or deletion on the Secondary node. 
• Uploading certificate files that have identical content to existing certificates installed on the NetScaler.
• Uploading/Updating certificate files that have the same filenames as existing certificates on the disk.