I was able to figure this out. I had modified my master page and each time I did, I would copy the current one, append the date to it and make the copy my active master page just in case I had to roll it back. This did cause the "Change the Look" section to look at my original seattle.master page and not the new one with the date appended.
To fix this, I had to create a preview file that had my new master page name seattle_20150518.preview. Then when I went to change the look, this new preview file appeared in the Site Layout and would let me apply any new changes.