Hi Conrad123.
I understand you are unable to print all the grid lines from excel.
I will be happy to help you.
Try creating a new file to see if it will print correctly.
If you are still having issues then I would uninstall and install the newest drivers for the printer.
HP Drivers & Downloads. Type in your product and select next, then select the operating system and click next. Click on Driver - Product Installation Software and download the drivers.
If you are still having issues please let me know.
Thank you for posting on the HP Forums.
Have a wonderful day!