iCal and Reminders sync Mojave

recently acquired new iMac Pro. trying to bring up my Apple ID calendars and reminders on the new beast. I have both old computer and iMac Pro logged into my Apple ID and iCloud, and iCloud prefs set to sync calendar and reminders. Trouble is, i don't get any of my Apple account iCal or Reminder content on either of those apps. And, now i get repeating error messages: "The server responded with "400" to operation CalDAVUpdateShareesQueableOperation"

Any clue how i resolve this error message and successfully sync iCal and Reminders across devices?

thanks.