Thank you for your suggestions.
I have two other devices, iPhone and iPad. All of them work fine with normal iCloud services. The only problem I have observed is signing onto the iCloud website with any browser I have tried. Signing in on any of these devices results in the same Communication error as described in my initial post.
I have not been able to try to sign in on any device via the browser.
I am not yet able to try to sign in from a different computer on a different network.
I was able to sign into my wife's iCloud account on my Macbook Air (and other devices) on our home network without a communications error. So my wife's account functions without a problem. My account exhibits the communication problem.
My computer runs Malwarebytes for malware protection. When I stop malware protection, the problem persists.
I would appreciate your further suggestions.
K Martin