Can't return borrowed item

I borrowed a book from the library, read it but when I tried to return it to the library I got this message:

{60C6EFC5-7D2E-4DC2-85A5-92470ED5EB15}Fmt818(1).epub is not open from library, would you like to copy it to library

I tried removing it from the library and re downloading it but it still won't let me return it!