I need help reconciling ADE on my PC with my Overdrive App

I have a pc with ADE downloaded to it. I recently bought a Kindle Fire 6. I downloaded the Overdrive App using the same email as my ADE. However, whenever I try to download a previously purchased book to my Overdrive account, it tells me it can't because I has been downloaded to another account. I used my email account for both so I don't know how to reconcile this.