BIOS update 1.20 broke my Vostro 5490, can't revert

I updated the BIOS on my Vostro 5490 to 1.20 today and now it won't boot to Windows. I tried the BIOS recovery process, and then I tried reinstalling 1.19 by downloading it to a USB drive on another computer and following the instructions in article 000132453, but that didn't help.

Every time I restart I get the blue "Automatic Repair" screen saying "Your PC did not start correctly" and giving me the choice of "Restart" or "Advanced Options". If I choose "Advanced Options" and then choose "Continue (Exit and continue to Windows 10)", the laptop restarts and I'm right back on the "Automatic Repair" screen.

Any suggestions? Thanks in advance.