Icloud can't establish a [secure] connection to the server
I cannot connect to Icloud with Safari 13.1.1 with IMac /High Sierra (10.13.6). I can connect with Edge (using now), Firefox and Chrome. I tried what I could for a few months. Apple id / passwords same on all devices.
Error msg for Icloud: Icloud encountered an error trying to connect to the server.
I could not connect to this page either with Safari: End of this the long error message says says "..... Safari can't establish a secure connection to the server "idmsa.apple.com"
I'd be thankful for advice. I've tried the general troubleshooting tips, but I have not tried reinstalling Safari. An older macbook pro with Sierra and Safari does connect.
iMac 21.5″, macOS 10.13