Hi to all JIRA lovers 
3 days stuck with this problem (my team mates have called firemans because of burning neurons smell in the office hehehehe):
I try to configure Permissions/Project Roles to be able to give issue to users (kinda hard to explain).
Example:
I use JIRA Service Desk (have JIRA admin rights)
user: jiratest
Member of groups: jira-users; jira-developers
Have Developers and Users access in Project Role
I have added: the group jira-developers and the user jiratest, in the permission schema (almost all the Authorizations - user can be assigned included) and still i have the error:
Impossible d'attribuer des demandes à l'utilisateur 'jiratest'.
= not able to assign issues to user jiratest
When i run Test Session (test for Users can be assigned authorization) for jiratest i got this: :
from french with Google translate *
The JIRA assistance crushed authorization.
Looking to perform an action reserved for agents on a help desk project. To do this action , you must be licensed to helpdesk agent and authorizations "Browse requests " and "Change requests" for this project.
The triky part: IF i add jiratest to service-desk-agents Group AND give access to Service Desk Team in Project Role THAN i'm able to assign issues to jiratest.
This is not ok for my needs, because we have a lot of external collaborators and we don't want to give them the same rights like our Service Desk Team.
I work alone for this project, i have 20 tabs opened in my browser, i really don't know where to look...
In advance BIG thank's from Belgium