iTunes purchases won’t download to iPhone

I have a continuous problem with my iPhone 16 pro when trying to download purchases which I’ve made on the phone from the iTunes Store. They don’t automatically appear, and so I go to ‘purchased’ and click on download, and the dial appears and nearly completes the download, then it reverts to the download cloud icon. This happens every single time.

The only way I can get purchases made on the phone appear in the phone library is to go onto my MacBook and download the purchase there. Once downloaded to the Mac, only then does it sync to the phone.

surely it shouldn’t be this difficult, why is this happening?

TIA.