Could you please explain a little bit about the Idle Time Scan settings in your Norton Antivirus for Mac. Did you check with the Idle Time Scan - Is it turned on or not? If not, please turn on the Idle Time Scan by going through: Automatic Protection --> Idle Time Scan [turn on] and Click on Conifgure for Idle Time Scan--> Select the option [Restore Defaults].
Restore Defaults will make the Idle Time Scan Settings go back to the default settings with the given options.
As you told, the manual scan and the updates are working fine, then we can check with the scan settings.
Also adding to the Idle Time Scan Settings, Please look at the logs and history about the Idle Time Scan for the exact issue.
You can click on "History" in the Norton Antivirus Screen, right next to the "Statistics". In the History window, have a look at the left panel and click on Antivirus Scan for history and under the Logs click on All.
I'm, experiencing the same. When I check the log, it says that the scan was cancelled. Manual scans work fine. I have the idle-time scans on and the configuration is set to default,
I experience the same problem..... the log says that the scan was cancelled. Maybe because I send the MacBook to sleep every time when I don't intend to use it for more than about half an hour?
For both of you, certainly this could be the reason, that the Idle-Time Scan is not completed in your Mac Pcs. By default, the Norton scans the entire system when your PC is in Idle and by the time when you are working or when your PC is going to sleep, the scan will be stopped [Here it shows "cancelled", because it was scheduled on a particular time and the same will be assigned for next schedule]
Then the scan will check with the history log to start again from where it stopped during the idle time. So, I am sure nothing to worry about this, because Automatic Protection is always turned on.
This Automatic Protection will keep on check with computer for changes like file create, copy or modify and it will perform a quick scan when any thumb drives plugged in and the network activities through your Internet.