I'm experiencing the exact same issue as described in JSDSERVER-1641 (https://jira.atlassian.com/browse/JSDSERVER-1641)
Running Jira v7.12.1 and Jira Service Desk v.3.15.1.
We have 3 support agents, and 7 jira users. The latter is mostly working as developers, that should be able to track time, comment and be assigned to issues on our 1 Jira Service Desk Project. However, we get the following explanation when running *Permission Helper* to try and find out why a user cant be assigned:
🛑Jira Service Desk has overridden this permission
The user must have a Jira Service Desk license and Service Desk Agent permission on this project.