This operation can be performed only on a computer that is joined to a server farm

 You need to update the web.config to show errors rather than giving the generic errors.  I typically use “RemoteOnly” I believe…

By the sounds of it, the user you used to install SharePoint doesn’t have the correct permissions on the database.

You should have a “farm” account and an “install” account.  

I typically have an “sp_admin” account which I use for general administration and installation.  Your farm account also has particular permissions.