It needs your 2017 AGI not your 2017 W-2 forms...your AGI is only rarely the total of your 2017 W-2 forms.
Try a zero for your 2017 AGI, if that doesn't go thru, and you if can't find your AGI from your actual printed 2017 tax files ...then you may have to switch to file by mail...then print them out and mail them in yourself.
Print them out EVERY year and you won't be caught in this situation.
An FAQ about where the AGI is located?..... here:
https://ttlc.intuit.com/questions/1900840-how-do-i-find-last-year-s-agi