Do not add @ folders to the path: add the folder that the @ folder lives in. So add C:\Users\minht\VinVEM\+Geometry\+Geo2D to the path
Classes within a package folder (begining with + ) are not automatically added to the path just because a containing package folder is on the path. That is, if the class was in C:\Users\minht\VinVEM\+Geometry\@Point2D then you would add C:\Users\minht\VinVEM\+Geometry to the path and the Point2D class would be found in that, but with your class folder being in C:\Users\minht\VinVEM\+Geometry\+Geo2D\@Point2D then MATLAB is not going to automatically look inside C:\Users\minht\VinVEM\+Geometry\+Geo2D to see if there are any class folders. Using the + package folder syntax does not recursively add subfolders to the path.
