2017 can not be efiled it must be mailed.
for 2018 try using AGI for 2017 of zero (since you haven't timely filed it) if that doesn't work what is the reject code for 2018. if it's for incorrect 2017 AGI then if zero doesn't work all you can do is mail it in. DO NOT mail in same envelope with 2017 and use a method where you can track delivery.
