Error: "8506,421" appears on my Norton product trouble

Hello

I have been trying to update my Norton internet security. Everytime I sign on to my computer I get the Error: "8506,421" appears on my Norton product. I have tried to uninstall and reinstall it as well as use the Norton Power eraser but it isn't working. It keeps going back to the error message. Any tips on what to do?

Thanks

Tom