======Overview======
This error is most probably when you try to configure log shipping on network location. Even though you might have access to read/write to that destination from the windows explorer, the SQL Server can still say that it doesn't have access. So in order to fix that you have to:

======Solution======

  - Grant access on the network location to Everyone
  - Change the service owner to service (default is NT Service) to either user who has access or the domain user.