"Error importing EPUB. EOCD not found. Not a ZIP archive? (Error Code 1068)"

Hi,
I made an .epub file which works well on iPhone.
When I try to activate it using "OverDrive Media" app on android I get this eeror message:
"Error importing EPUB. EOCD not found. Not a ZIP archive? (Error Code 1068)"

Tried googling it but can't find anything...
Any ideas?

Thanks :)
Oren