Failure for Mac Mini calendar to Sync with iCloud calendar
I synchronize my calendars through iCloud over three devices: a two-month old Mac Mini, an iPhone 12 and Mac Air M1.
Starting recently, entries on the Mac Mini calendar don't show up on the iCloud calendar (or the other devices). Calendar entries on both the iPhone and the Mac Air show up on the iCloud Calendar (and each other). I believe I have correctly checked the boxes to set up the connection between the Mini Calendar and the iCloud Calendar.
For what it's worth, each time I use my Apple ID and password to sign into iCloud from the Mac Mini, I get a message saying I am signing in from a new device even though it is only an hour after the previous sign-in. Thanks for any help.
Mac mini, macOS 13.2