Hi @rj891852,
Thank you for your updates!
Firstly, I apologize for any inconvenience or difficulty you had when following our documentation to assign your user to a role using an Action.
However, I am glad that you were able to get it working! Would you mind sharing some details on what you did to get this working with the rest of the Community?
I see in your tenant now that you have used the code provided in the How can I use the Management API in Actions? FAQ, and chosen to use a Post-Login Aciton instead 
.
Just a friendly reminder that when testing the action script, please remember to sign up a new user each time. It seems that the tests you performed yesterday may have used the same user each time, which might explain the issue with role assignment. I also noticed an increase in the number of users in your tenant today, which might have contributed to your successful tests.
Thanks,
Rueben