When you find some file sharing issue with your Skype; you need to make sure that you are following the basics of Skype file sharing. This includes the file type, size and format. Along this your internet speed should be decent enough to get it deliver properly. You should make sure the file which you want to share shouldn’t cross the 300 MB limit. Your friend should have the enough space to store your shared files, else it won’t deliver.
Read here :- http://techhelpcontact.doodlekit.com/blog/entry/4201870/how-to-configure-setup-skype-in-windows-10