Ebooks not appearing on digital editions

I have downloaded some ebooks from my local librarys borrowbox and have uploaded them to my digital editions account to use on my kobo e-reader. I want to delete those ebooks from my account so I can return the ebooks to my library but when I plug in my ereader, the ebooks dont appear. Please can someone advise what I should do? I have uninstalled digital editions and reinstalled it and also i have reauthorised it, nothing has worked so far. Thanks