Dear respected EarlS155,
Good day! Thank you for posting to Microsoft Community. We are happy to help you.
As per your description, I think you mistakenly, turn on " Focus Cell" feature. Cand you please try in Excel file>click on View tab>select Focus Cell button to toggle off.
That's a new Insiders feature called 'Focus Cell' described in the blog post in the link below: Increase ease of navigation with Focus Cell in Excel
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Waqas Muhammad