I had been running the Backups program successfully in Lubuntu 18.04.3, in order to backup the Home folder to an external drive (which has plenty of space on it).
The Backups program worked successfully for several months. For the last 318 days now, though, the daily attempts of the Backups program to perform backups automatically have failed. And the Backup Now button is grayed out. (Since then until now, I was too overwhelmed to get engaged on this web site to try to get help to fix the problem.)
I am a relative newbie - and almost always I use GUIs. I can perform Terminal commands IF they are provided together with complete and precise instructions.