Problems sending Rise files

We have 2 people working on a large project and need to share Rise source files. When we use the share a copy function, the courses do not always appear in the recipient's Rise screen.  The recipient's email address is the same as her Articulate 360 account, and is the same as the times when the share function does work, so we have eliminated that as a potential issue. How can we get this function to work consistently?