SSL Certificate error is received when opening the Citrix Receiver or when checking for updates.
Citrix receiver: Certificate Trust Issue There is an issue with the self-signed certificate on the Citrix Receiver Merchandising Server at x.x.x.x. Citrix updates are not available until the issue is resolved.
Install new SSL certificate to replace the expired certificate.
The Certificate Chain includes an expired certificate.
Microsoft Technet Blogs - Installing a Self-Signed Certificate
Installing SSL Certificates.