Solution ID : SO26942
This error may occur when an older version of Citrix Receiver (ICA) connects to a Citrix server with SHA-256 SSL certificate installed. The Citrix Receiver (ICA) installed on a Windows client system does not support SHA-256 signature algorithm and will need to be updated.
To resolve this issue, the Citrix Receiver (ICA) on Windows client system must be running a minimum version of "Receiver for Windows 3.4".
No changes are needed to the certificate as this is a client error only. Once updated the client will be able to connect.
For more information about Citrix Receiver for Windows, visit Citrix product documentation website.