Thank you for taking the time to report this issue to the Community, although I apologize that you have not yet received a response.
If you are still needing assistance with copying/pasting a paycheck transaction in Quicken, please take a moment and review the information available here, and post back to let us know what version and release of Quicken you are using.
Please also let us know what steps are being taken to duplicate the paycheck transaction.
Are you right-clicking on the original transaction and selecting "Copy" from the menu that appears? Or using the keyboard shortcut keys of Ctrl + C to copy and Ctrl + V to paste?
The more information you can provide regarding this issue will help the Community to better understand and assist.