Why can't I see certain fields in JIRA?

Atlassian have made some UI updates to the issue view. With this update, some data fields have been removed, such as the Issue links section.

You can still revert back to the old view by clicking the 'See the old view' link at the top of the issue. By doing this you should see the Issue links section containing the link back to the ProdPad Idea or User Story.