Dear Margaret,
From your description, it seems that Ctrl+C and Ctrl+V don't work when you copy and paste the Excel data from Excel for the web to a local document.
If yes, please check whether the data you copied are showed in Clipboard in Word.
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I suggest you open the clipboard in Word>click on Clear All to clear all cache, close the local file, clear the browser cache, close the browser and then log into SharePoint Online with your account to open the Excel file and open the local file with Word at the same time and do a test again to see the outcome.
Welcome to share any updates at your convenience.
Thank you for your time and effort.
Sincerely
Cliff | Microsoft Community Moderator