Error while installing updates 3.0

[bobw]

I have just installed LL3.0 but cannot install updates.  I have tried 2 separate repositories.  The system is as installed - I haven't installed any other software.  The error message that I am getting in the terminal or Synaptic suggests that the fault lies with LL:

"The repository 'http://repo.linuxlite.com/linuxlite xenial Release' does not have a Release file.Data from such a repository can't be authenticated and is therefore potentially dangerous to use."