To be clear---do you mean you used the online program for a 2017 tax return? If you did that, it was a big mistake. The online program is for 2019 returns--no other year.
Or did you go to a 2017 return you began working on a couple of years ago and print it to mail in? A 2017 return can only be filed by mail.
We need to know what you did in order to help you. Please tell us all the steps you have taken with that return.