iPad Pro M2 Photo Library Not saving photos from Photostream even though Photostream is working?

Just noticed that whilst the photo stream is working between my iPhone and iPad (ie photos from iPhone are appearing in the photo stream on the iPad) for some reason the photos are not being saved into the photos library on my iPad Pro M2. It was working properly up to 12th December, but no photos have appeared in the library since then.

In addition there is no "Hidden" folder even though it is turned on in settings - it simply is not there under utilities or anywhere else.

If I click a recent photo in photo stream and then “show in all photos” it takes me to the library but the photo isn’t there.

There is plenty of storage left on my iPad.

I’ve tried restarting the iPad.

I've tried resetting the iPad settings, neither have made a difference.

If I take a photo with the iPad camera directly it DOES show in the library, its only photos from the Photostream that are not being saved (or show) in the library, although they CAN be seen in the iPad Photostream.

I don’t use the iCloud for storage of photos, just photo stream.

I’m on iPad OS 16.2, M2 iPad Pro. 

Anything obvious I can do please or something I’m missing or is this going to need a full reset of the iPad and start with a fresh install?