How to resolve "Failed to create JIRA ticket: Field 'assignee' cannot be set" errors?

[Nic Tolksdorf]

Confluence user license was temporarily switched off for a user account while their Jira license remained activated. However, calls to the Jira REST API to create Jira issues started returning the following error:

"Failed to create JIRA ticket: Field 'assignee' cannot be set. It is not on the appropriate screen, or unknown."

Confluence user license was switched back on for this user account but the above error message continues to be returned when attempting to call the Jira REST API to create Jira issues.

[Nic Tolksdorf · Accepted solution]

We've worked around this error by removing the assignee field from calls to the Jira REST API to create Jira issues. The unassigned assignee field is now automatically assigned the project's default user in Jira.

[Nic Brough -Adaptavist-]

If you log in as the user the REST calls are authenticating as, do you get the assignee on screen when you start creating an issue?

[Nic Tolksdorf]

Yes, the assignee field appears on create screen when I log in with the same user account as the REST calls.