Cannot Update my 2012 Macbook Pro
So I have been using my macbook pro for a while now and had no issues, it was operating on high sierra and worked well. I did a factory reset because I wanted to clear all the files I no longer needed and now I can't update past Mountain lion. The update isn't in my update section and every time I try download it it either says my Apple Id hasn't been used with the app store and that I need to update my mac to use it (which is what ik trying to do) or that the download had a corrupt image. I have tried everything and its just not having it!