FM 12: Automapping failed

I am using FM 12 to generate Responsive HTML5.

All the actions I'm describing take place here:

I assumed that I would be able to map any paragraph style from my original FrameMaker template to an equivalent Output style. Here is what I have tried:

1. The mapping seemed obvious enough, so I initially manually mapped a few items that were easy, like my H1 to Heading 1.
2. Then I realized that many of my original template paragraph styles did not have equivalents in the Output styles list.
3. I reread the FrameMaker 12 documentation and clicked Paragraph at the top of the Styles panel, selected the Automap Paragraph Styles checkbox, and clicked Save.
4. Filled with hope, I then clicked the original template style, say Bullet2, that  I wished to map.
5. Alas, the Output Style field said [Automapping failed. Add StyleName to the CSS].
6. I then reread the documentation some more, exported the styles from the original FM template to a .CSS, and then imported that new .CSS back into the project (in other words, clicked Export Styles, waited a reverent moment, then clicked Import Styles).
7. Repeated Step 4. Same result.

What am I missing? How do I map FM styles to a style for the Responsive Help output?

Thanks.