I fixed the issue with Safari "Safari can't establish a secure connection to the server" *FIXED

I followed and tried multiple posts, without finding a real solution. The issue resides with the "login". The "certificates" and the website's associated "identity preference" in Keychain Access. The certificates and the association are either are either old or corrupted. I closed Safari after deleting Safari's cache and web history. Opened Keychain Access. Selected the "login" in Keychains (left panel) and "All Items" in Category. I sorted the list by "Kind" and deleted the website "certificates" and the website's associated "identity preference". Close Keychain Access and visit the website in Safari to renegotiate a connection. Go back to Keychain Access and look for the website's certificate. Open the certificate and under "Trust" look for "When using this certificate:" Select "Always Trust". You should be good to go. I hope this helps