Can an external user be a Service Desk Agent?

[Unknown User]

I have added an external user as a Service Desk Agent, and they do receive the JIRA invitation email. When that user clicks on "Join them now", they are directed to our Service Desk portal. 

The external user appears to be correctly setup in JIRA User Admin, and says Pending Invitation. 

I presume its possible to setup external Agents but something isn't working for me.

Thanks for any help!

[Jack Brickey]

it sounds like the user is still configured as a Customer. Check the following:

1. project > customers and search there for the user
2. jira settings > user management > portal only customers and search for the user there if not there
3. jira settings > user management > search for user and verify the user is listed there and that they have Service Desk checked