Hi Megan3189,
That error message usually pops up if someone else is editing the same transaction, but if that's not happening, it could be because of the “warn for duplicate purchase orders” setting.
You can check this by heading to Setup > Preferences, then going to the Purchases tab. Try turning off that setting and see if that sorts things out.
If the error's still hanging around after that, just jump onto MyAccount to log a ticket, or have a chat with us live through MOCA (our virtual assistant), and we’ll dig a bit deeper for you.
Regards,
Genreve