The books from my Adobe Digital Editions app won't sync up and load on my E-reader

I recently got a Pocketbook and would like to move some books I have on my Adobe Digital Editions app to my e-reader. 
About a day ago a book I had on there synced up after just a few hours and was available for download on my e-reader too, which I was very happy about.

But now I've been waiting a good 24 hours for two new books to get synced up on my PocketBook as well and nothing has happened.
I attempted logging out and in again on my e-reader, but it hasn't worked. 

What do I do?