TextExpander won't sync via Dropbox

I've got TextExpander installed on my iMac and MBA. Both computers are connected to my single Dropbox account (though the Air is only connected to two folders, one of which is the TextExpander sync folder).

For some reason, even though I have chosen sync via DB in TextExpander prefs on each computer, they won't sync with each other. Instead, two files appear in the Dropbox folder - one for each computer.

Anyone else experience this, and anyone figure out a fix? I want to install the program on my work iMac and iPad as well, but don't want to until I've got this figured out.

Thanks in advance for any help!