I have a mac mini running El Capitan w/a 6TB ext HD for Time Machine.
It keeps acting like its preparing a backup, but it hasn't actually done a backup since late Feb 2020
The HD had about 1/2 TB of open space and a full bkup would take 2.6 TB.
But Time Machine is supposed erase old backups as it stores new ones.
I dont see anywhere in prefs to make any decisions in this direction, so I am confused why its not backing up.
Appreciate any help / suggestions.