Hi foxview,
Sorry for the inconvenience caused by this issue.
Per your description, I want to suggest you try these ways to see the results:
1. Update your Office. Go to Excel-> File-> Account-> Update options-> Update Now.
2. Try to run Excel safe mode.
3. Try to use Ctrl+U key-bored to copy content.
If the issue still persists, we want to collect related information to move further:
1. Can you provide the screenshot about your Excel version information? Excel-> File->
Account-> Product Information. Please remove the email address on it.
2. Does this issue happen to all Excel document?
3. What content you wanted to copy? Can you take a screenshot about your content?
4. When did it happen? What did you change before this issue?
I found some threads have similar issue, for your reference:.
Clipboard
problem in Excel 2016
Excel 2016 - “There's a problem with the clipboard, but you can
still paste your content within this workbook." Neha's summary.
Regards,
Ivy