Watchlist sync on Apps

Hi, I was wondering if anyone could give me some tips, please?
I log into my Trakt account via apps such as BeeTV or Cinema. I can click an option to sync with Trakt, but when I go into my Watchlist or Favourites on the app the only things that appear are what I have manually added. None of the items I added to my watchlist via the Trakt website appear.
So I have to manually find them via the app.

That’s more of a question for the app developer. It’s hard to give any feedback without know how they use the Trakt API.