Thank you, webworkings. I very much appreciate your prompt reply. Microsoft has now elevated the problem another level from L2 to L3. I will be working with an engineer tomorrow on it. Will advise what the outcome of that is.
UPDATE: The problem was mainly with Windows 10. The Level 3 tech at Microsoft reinstalled my Windows 10. That cleared up the problem on most of my worksheets in Excel, but some files on OneDrive were and still are corrupt. For those, I am pretty much not using them anymore. If and when I do, I can do so by using OneDrive Online, use my desktop, or by using a copy directly from my laptop's hard-drive. Good enough. Thank you for your assistance.
webworkings :
The problem likely has nothing to do with the computer. It is OneDrive itself that has the issue. I would contact their support and have them look into the issue.