1 - Go to a Requirement issue type (Story, Feature, ...)
2 - Create New Test
3 - The Test does not appear in the Test Coverage
The sequence of the list (Issue Linking) should be the root cause of the problem.
1 - Go to our issue Linking (Jira Administration -> Issues -> Issue Features - Issue linking) and change only the "Outward Description" to something like "Xtests" (you can choose it as you prefer)
2 - Do a re-index of your Jira Instance
3 - Now Go to Jira Administration -> Manage apps and there you need to Disable and Enable the Xray app (This step is crucial)
4 - Try again to Create a New test from the Requirement and let us know if it's working now.