Why are Apple Intelligence models not downloading on iPhone's hotspot but work with Wi-Fi?

When Apple Intelligence was first available with the new MacOS update. The Apple AI models were not downloading on my iPhones hotspot, which is use to run internet on my Mac. The AI models showed 0% downloaded for many days, on iPhone's hotspot. One day when I was connected to wifi, then the AI models were able to download, and ran smoothly. But now after a few months, the AI models are again showing that they are 0% downloaded, and not downloading on iPhone's hotspot, but new siri is running perfectly fine. But Image Playground and AI writing tools are not working.

I would like if I am able to download all new features on my with iPhone's hotspot.