CookieThief

Hello Everybody, I am aware that this thread is from 2 years ago, but I just encountered the same problem. In order to solve this I went into edit mode with the object in Blender 2.83 and pressed "a" which selects all faces / vertices / edges, depending on what select mode you are in. The entire object should be highlighted. I then went to "Mesh" (see images), went to the "Normals" section, and selected "Recalculate Outside". This probably will not fix any edges that are not merged, but it will fix the faces that are inverted on the object. Hope this helps anyone with this issue.