Do not transfer the 2017 info you have into the 2018 return since the accountant did not use it... it only makes the situation much more difficult. Instead you will need to enter it from scratch and when you have the original return exactly as it was filed you need to choose to "mail" in the return in the FILE tab then close the program. When you reopen it the option to amend it will be available ... then make the changes you need to make although not sure why you did not return to the accountant to have the 2018 amended.
