I have an external user who I permissioned with as an "editor".  He was able to accept the invitation link and sign in. He can see the contents of folders and was able to create new folders, but he cannot up load files to them.  Tried 4x and failed each time.  This is a C-level executive so don't have time to do a lot of user troubleshooting with screen shots and such.  Any diagnostics that can be run on the back end to identify the problem?