Books app. Sync and underline

[AC Question]

I just got a Samsung S6. I use and download and underline study in the books app. All the time. It has always synced the books and underling between phone and my Samsung tab S tablet. Now it shows up in books in both, but the underling don't show up except in the one I underline in, it don't sync that anymore. And it always has with my other phones. Help? I nice guy at a phone repair place spent a hour the other day and still no underline syncing