Unable to @mention Customer or Request Participant in Next-gen Jira Service Desk

Summary

When adding a comment to a Next-gen JIRA Service Desk request, the @mention feature does not work for customers or request participants. unless those users have made a comment on the issue.

Steps to Reproduce

1. Have a customer create a request
2. As an administrator, view the issue in the Issue Navigator
3. Type a comment and use the @mention feature to mention the customer

Desired Results

• A list of suggestions will appear which you can choose the customer or request participant

Actual Results

• A list of users appears but this list does not contain the customer or any request participants
  • Any customers and request participants who are agents or collaborators will appear.

Workaround

• Have the participant to make a comment. They will be only mention-able in the issue which they made comment.