iWatch6 won't synch with Audible books

My IWatch 6 has stopped synching books from Audible. During the "synching" attempt, I put it on its charger next to my iPhoneX which is also plugged in. I was able to listen to books though my watch until recently. I removed those books after I finished them, but have been unable to synch additional books. Please help. this is the reason I bought the watch in the first place.