Ok so I figured out why some people have had an issue still. Just follow the steps everyone above is telling you to do but just change the start date to significantly further back. I had this issue as well and it was because I drew up the invoice before I ever entered the product onto my quickbooks account. Therefore when I tried to save the invoice it wasn't updating the transaction date to the current date so it was giving me that error message. So make sure the start date is pushed back before the date that you initially drafted the invoice and you should be good to go!