We have been using the + button on Epics to create "Child work items" under the Epic or to make already created tasks into "Child work items" for the Epic. In the same vein, on a task, we were able to use the "Add Parent" button to select an Epic to add the task under.
Recently, these functions have stopped working and we don't know why. Help please!
P.S. - We are still able to create sub-tasks from tasks though.
Edit - changed "Project" to "Epic" to use Jira terms.