Hi @Valerie TV,
Firstly You could try clearing the clipboard to see if it resolves the issue.
Click Start > Settings > System > Clipboard > Clear (under Clear clipboard data).
Also have a try to use the shortcut ctrl + C and ctrl + V to copy and paste.
Clicking Paste Special... and see if it works.
If the Paste option works in the Safe Mode, enable your Add-ins one by one until you hit that one that is causing the conflict. Leave that one disabled or uninstall it. For more information, see Adding or Removing Add-ins and Working with Office Safe Modes..
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