Audio playback position not syncing across devices

I have long audio files in iTunes for windows; they are under 200mb per file.

I have an apple music subsrciption.

I have 'sync iTunes library' turned on and these files show on Apple Music on my PC, iPhone, iPad and cellular watch (apple watch series 9).

They have 'remember playback position' ticked in the options section of the files.

'Sync playback position from across devices' is turned on in the Store tab in settings.

The PC is 'authorized'.

The files are arranged into playlists, which is how i access them from the iPhone, iPad and watch. They are all uploaded.

The playback position does not sync across devices; I am 2 hours through a 4 hour audio file on the PC, which the PC remembers. They start from the begining of the file, on all other devices no matter what i do.

All devices are running the current software;

All are signed in using the same Apple ID;

I have turned off sync library, then turned it back on on the PC and iPhone;

I've restarted all devices;

I've waited overnight for things to sync;

I've left the sycn to happen automatically and i've prompted the sync in iTunes.

What am I doing wrong and how do I get the playback position to sync across devices?

Please help!

Thanks.