How do I generate a report showing the status of all test cases in a test plan?
TER listings only report on cases which have results. These reports do not show the all-important remaining tests which have not been attempted.

You need to create TERs for all the test cases in your test plan. Once the TERs are created, then you will see these in the TER reports as not having started. You can determine which of the Test Plan's test cases don't have TERs by viewing the Test Case section of the Test Plan. There's a column in the Test Case list table of the Test Plan that looks similar to the Generate TER icon. If you don't see it then you may have to modify the Display Properties for this table to add it. In either case if you hover over that icon it will say "Number of TERs associated with the current test plan". If there's a 0 in that column then that test case doesn't have any TERs for this plan and you need to select such test cases, then click the Generate TERs button. Once all of your test cases have been plan for execution via a TER associated with this plan, then you will see the not started TERs accounted for in the reports.