Hi Heather,
I’ve checked your sidebars, you were doing it right except that you have chosen for the Blog sidebar “sidebar location” <u>”As Main Sidebar for selected Post Types blog”</u>
I’ve created a test sidebar through the theme options, and selected that sidebar from Theme options > Pages Settings > Category page, instead of the Blog sidebar. and it worked fine without defining “sidebar location” from the the widgets page.
Hope this helps,
Thanks