iBooks not syncing iCloud PDFs and ePubs to iPad.

Hello, I have an iPad 3 running 9.3.5. Up through 9.3.4 iBooks used iCloud to sync ePubs and PDF files without any issue. However, since upgrading to 9.3.5, it looks like iBooks can't see any of my iCloud files (except those books bought through the iTunes store). My Mac (10.11.4) sees the books and can download them, and my iPhone 6 (also running 9.3.5) can see them as well. Weirdly though, if I bring up iTunes it can't see the files--even those that I've purchased through the iTunes store.

Any ideas? I'll try to reload the iPad, but I don't know what else to do. I've turned iBooks on and off in the iCloud setting a couple of times to no avail, and of course restarted a few times as well.

Thanks,

Dan