Oh, that can happen because you have imported an open mesh file. 3d scanning without any further postprocessing always results in mesh models. They can be either open or closed ones, that depends on a lot of things.
I am sorry to say that but you will have a really limited ability to edit mesh models. Shapr3D is a CAD modeler software which means it works well with BREP models, which have a totally different mathematical background than mesh models. For editing your mesh files in Shapr3D, please take a look at this article: