Every time I type sudo apt update this information appears: The box was unticked when I check the software and updates
elizabeth@elizabeth:~$ sudo apt-get update
Get:1 http://security.ubuntu.com/ubuntu bionic-security InRelease [88.7 kB]
Hit:2 http://gb.archive.ubuntu.com/ubuntu bionic InRelease
Get:3 http://gb.archive.ubuntu.com/ubuntu bionic-updates InRelease [88.7 kB]
Get:4 http://gb.archive.ubuntu.com/ubuntu bionic-backports InRelease [74.6 kB]
Fetched 252 kB in 1s (175 kB/s)
Reading package lists... Done
Is there a fix?
Open software and updates and uncheck the option Installable from CD-ROM/DVD