Adding User Shows "Please fill out all required fields."
Android Galaxy S7. Just loaded it from the GitHub today (my first SmartApp).
When adding a user, I get the error message "Please fill out all required fields."
If I keep hitting the done button, i keep getting the error.
If i go down to the bottom, and click the lock in the Locks section, then hit done, and then hit done, it usually works. (Out of the 6 times I tested that, it worked on all but 1 of the attempts, and that one took on the second try)
Here's a bogus user showing the error:

Anything else I that would help diagnose this?
Try expanding "setup" at the bottom and see if the "Select slot" is selected.
I had this same issue. If you mess around in the app section for a short time including expanding setup as @schaitanya mentioned, it will eventually work
Android Moto z play. Just loaded it from the GitHub today (my first SmartApp)! Your directions were great. This issue also happens for me, if i disable the user (wait till the user isn't active) and then enable them, it works.
I had the same issue and go around the issue by Clicking into Schedule (optional) and click Done. Then the user was saved successfully.