Option to link a Jira project is not available

If the option to link a Jira project is not available in the projects External Apps tab, check with a system Admin to ensure third party app integration is enabled. A system admin can enable Jira integration in their Admin module in the secondary tab External Apps. 

Note that only Project Owners can link projects from third party apps. Project members other than Project Owners will not have this option available or visible to them.