Review says I'm good to go, but I still can't E-file

Turbotax says "E-File is not available because your tax return includes forms that can't be e-filed. Revisit the Review section to see which forms." 

When I visit the Review section, I get the notification saying "You're good to go!" and the green seal that says "Ready to file". It says nothing about any documents that can't be e-filed.

I read someone else's similar question, and it was recommended that they clear their browser cache. I've already done this, but I still only get the File by Mail option. This is an issue because my state will not allow me to file electronically completed taxes by mail, so I have to e-file my state taxes.