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.

touchor create files where you want to store your backups) to ensure nothing has changed 318 days ago. Is the file-system being used to store your backups to POSIX compliant? or a non-native file-system? – guiverc Jan 02 '21 at 22:10rsync& terminal tools common to all Ubuntu systems), nor see any with https://packages.ubuntu.com/bionic/lubuntu-desktop (I suspect you've added it and it's not a default program). I'm guessing your external WD drive is NTFS thus non-POSIX (unless you re-formatted it) so as I don't know the program, and it's a foreign fs I'd explore as per my prior comment. – guiverc Jan 03 '21 at 10:00pcmanfm) and navigate directory where you save your backups, and try to create (touchis the command, but you can right-click and Create New and select "Empty File" which is thetouchcommand). Does this provide any clues? (ie. error messages). I prefer commands as the error messages are easier to see errors when they occur, a quick play with copy/paste & create-new (touch) both had errors visible & not visible – guiverc Jan 03 '21 at 10:13backupis likely how it appears in menu but there are many - https://help.ubuntu.com/community/BackupYourSystem) I can't advise. I'd expect log files provide your answer (or clue leading to answer), or I would run the program from command line so messages appear on screen. I'd also explore system logs (dmesg,journalctllooking for clues). I'd also explore /var/crash/ looking for anything there (if the program crashed; clues will be found there). I would check you have free space too – guiverc Jan 04 '21 at 21:33Execline in the Desktop Entry. You may want togrep -Ri backup /usr/share/applicationsto figure out which file it is. Thengrep Exec /path/to/file.desktopto get theExecline. That will tell us the executable. You can usewhich executableto find its path. And you can usedpkg -S /path/to/executableto find out which package provides it. – wxl Jan 04 '21 at 21:44/var/log/apt/and may go back >318 days.. but that'd not be fun to explore – guiverc Jan 04 '21 at 21:44/usr/is a special Linux directory, and is not related to "user" files in Linix (they are in /home/). https://help.ubuntu.com/community/LinuxFilesystemTreeOverview refers to "/usr" as "/usr contains the majority of user utilities and applications, and partly replicates the root directory structure, containing for instance, among others, /usr/bin/ and /usr/lib" I'm aware of Deja Dup but having never used it, I can't offer any advice sorry. – guiverc Jan 13 '21 at 01:40