I've had the same issues with the log book not syncing on both my and my wife's watch. Tried force quitting both apps (phone and watch), logging out and it, updating operating systems, restarting phone and watch in alternating order, restarting and opening the apps in alternating order... no luck, logs still not visible in the app. Finally I tried un-installing and re-installing the app, which deleted the dives completely. Also had trouble with some settings being reset.
This is very unfortunate because I really liked the readability of the watch underwater and the interface. It's disconcerting to me as well that, even with the Apple monster behind them with this flagship-type feature, Oceanic can't seem to fix it. Hopefully they don't struggle with the same problems with the computer built into the new phone housing.
I think the AWU/Oceanic+ has a lot of potential, but certainly not ready for prime time. Luckily we were using as a backup for Perdix 2s which, I hear, are half-way decent computers.