Greta, you may need to do the REFRESH updates if you haven't done that with 2018 lately, I know I had issues with 2018 amended returns last month and I had to go through REFRESH updates to make it work properly.

They also stuck a 2019 box on that 1040X (no clue why!) so be sure you are checking the 2018 box, not the first one that says 2019.