Just to complement Nic's answer, Service Desk 2.x is only compatible with JIRA 6.3.5+ as described on the URL below. In case you're using a lower version you'll need to upgrade JIRA to at least 6.3.5 version.
Hello Atlassian Community! I'm Teresa, the Product Marketing Manager for Jira Service Desk Server at Atlassian. I'm excited to announce two exciting releases for Jira Service De...
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