I saw the latest post on this thread, went in and updated the MS Excel app on my iPad and - yes - all the functions of the pop-up menu are back and working!
Thank you everyone for your contributions to this thread! I have been following it since I lost these features, and have tried all the recommendations you guys have suggested - so at least I felt like if there WERE something out there I could do to fix it - I was doing it. And who knows when I would have found the app had updated without these posts! So thanks again from Indiana for all the help!