The title of your question is "Migrating Kentico 8 Website". Did you actually do an upgrade from v7.x to 8.x or did you simply move your instance from one server to another?
There is a good chance that the sql user doesn't have dbo access to the objects that were created. OR if you changed the schema from dbo to something else it could have issues with that. If you're on a shared hosting provider sometimes they don't give you dbo access so they create a schema (typically based off of usename) and assign those newly created objects to that schema.