I have CITRIX Client on my Windows 7 machine and am facing this error.
I think the Citrix on server is using SHA-256.
My Citrix version shows as "220.127.116.1110" in Add/Remove Programs.
I tried adding site to trusted sites.
I imported following certificates:
-- RapidSSL CA
-- RapidSSL SHA256 CA - G3 (I cannot find the certificate "RapidSSL SHA256 CA - G4" anywhere.)