An update.
I just found and followed aome instructions I found online.
(1) https://support.norton.com/sp/en/us/home/current/solutions/v58346509_EndUserProfile_en_us
(2)
http://community.norton.com/t5/Norton-360/Backup-Destination-Won-t-Work-after-Upgrade-to-5-0/td-p/488432
(Poster: yogesh_mohan) Re: Backup Destination Won't Work after Upgrade to 5.0, 07-14-2011 04:22 AM
In the Norton 360 main window, move the mouse pointer over Backup, and then click Manage Backup Sets.
On the Summary tab, under Things you can do, click Create new backup set.
In the window that appears, type a name for your backup set, and then click OK.
On the What tab, under File Types, select a file category.
On the Where tab, click Refresh and then select the your external drive.
In the Manage Backup Sets window, click Save Settings.
Essentially the same instructions. I followed them, first creating a new data set (Picture).

The first time through, I hadn't noticed I hadn't checked all the "Sources" boxes in "What". (See Picture) so it ran as My Documents. I didn't know if this made a difference.

IN "Where" the removable hard drive (F:) was already checked, but I refreshed the list anyhow, and re-clicked drive F: as the destination. I saved the Settings.
I then ran the Backup. It finished, saying it was completed with a little green tick, BUT the "Big Red Problem To Fix" signage remained on the Manager window.
I then refreshed and clicked all the "Source" boxes under "What", again went through the "Refresh/choose F: drive" ritual in "Where" and saved settings. (Picture)

I repeated the scan (as I've done MANY times more tonight than the two or three times this post suggests - each time usually getting a green tick and assurance Backup was completed). This time, again, I got a reassurance Backup was completed. And, again, the "Not recently backed up" signage remains. (Picture)

I've tried backing up to DVD but (whether it's my computer or what) it keeps saying there's no valicd disk in the computer and please insert one. Gave that away as a bad joke.
Any suggestions?
Please??????????????
ausgumbie