You can still get to the old library page here
https://www.kobobooks.com/library/library.html Ferrywoman posted that in the Kobo deals thread.
The sort problem for me seems to be the books that Kobo no longer sells have a date of 4/20/2016 and are always on top no matter what sort I choose.
I don't have many Sony books so I won't worry about them, but the old library shows that I have 191 books and the new only shows 183. If the sorts worked it would be a lot easier to compare.
Edit: the books Kobo no longer has don't seem to be the problem. I had guessed that might be the problem when I couldn't see the date added column.