how can i get this to work again?

The below Remembering play back solution no longer work after downloading ios 16.4.1 on my iphone.

If you add audio to your iTunes Library:

• as an Audiobook, iTunes will mark it to Remember Playback Position
• as a song - and leave it as a Media Kind is Music, it will not have Remember Playback Position turned on (so you will have to do it manually)
• and then change the Media Kind is Audiobook, iTunes should change the Remember Playback Position to on and lock it so that you cannot change it

I suspect therefore, that you may have imported the audiobooks as straightforward audio and they remain in your Library as Media Kind is Music, so iTunes thinks they are songs. You can set any song to Remember Playback Position. In your iTunes Library, highlight the audiobook and use the Edit/Song Info/Options>Remember Playback Position (and tick the box). If you use this method, I suggest that you also set Skip when shuffling, so that the audiobooks do not start playing when you are playing your music in Shuffle mode. (The setting is just below the Remember Playback Position, see the screenshots below.)