adobe wont let me download ebook because it says i have authorized a different account, but i only have one account.

I have tried downloading an ebook  both on pc and ipad and it wont let me because it says my ebook was originally downloaded with a different account. but i only have one account. I have tried all my email addresses to see if i have a different account or adobeID and none of my emails correspond with another account. how do i fix this problem? i paid $50 for a textbook that i can not read because adobe says i have authorized an account i dont even have.