After updating to 11.1.2 I could no longer use Time Machine to backup my iMac. After selecting the backup disk in Time Machine box the local address did not lite up. I had been able to continue Time Machine backups with my Mac Power Book, however, which I hadn't up dated with the new Norton update download.
The problem appears to be with Norton Firewall feature. There was no indication that the Norton Firewall feature was blocking the link but the Apple technician happened to turn it off and the link then was made.
I now operate with the Norton Firewall feature "Disabled" but with the other features "Enabled."