To be able to share content on Box externally you have to take Box 100 course (just have to watch a 5 min video)
https://it.uclahealth.org/support/guides/guide-for-box
“Upon completion of this course, external collaboration will be enabled for your Box account within 1 business day.”
NOTE:
Mednet Box considers other UCLA personnel to be “external collaborators” so you have to complete the above course to be able to share with anyone with an `@ucla.edu` email address.
For some reason you have to remove the “g.” from the email address otherwise the recipient will not get access to the shared content, despite the invitation going through. ie name@g.ucla.edu needs to be name@ucla.edu