Hi gaunab.

If you have the Terminal already installed then cd to /etc/apt/sources.list.d, then do an ls, inside there should be a file named n9repomirror.list.

I just checked up on coderus backup repos and it all seems to be online.

If the file n9repomirror.list exists then I think maybe step 2 didn't finish correctly, try running this step again a couple of times.

Also, i think it's better to enable Developer Mode from Configuration -> Security -> Developer Mode