Hello jeeyong,
Welcome to Apple Support Communities!
We want to help get the Personal Hotspot working as expected between your devices.
We see you viewed the Apple Support page for How to set up a Personal Hotspot on your iPhone or iPad - Apple Support
Start with these steps to help isolate the issue causing the error:
"Use these steps first
Try connecting again after each step.
- Check that Personal Hotspot is turned on in Settings > Personal Hotspot. If you can't find or turn on Personal Hotspot, check that your wireless carrier enabled it and that your wireless plan supports it.
- Restart the iPhone or iPad that provides Personal Hotspot and the other device that needs to connect to Personal Hotspot.
- Make sure that you have the latest version of iOS or iPadOS.
- On the iPhone or iPad that provides Personal Hotspot, go to Settings > General > Transfer or Reset [Device] > Reset, then tap Reset Network Settings."
This Apple Support page has the full details and even more steps to take: If Personal Hotspot is not working on your iPhone or iPad (Wi-Fi + Cellular) - Apple Support
We hope these steps can help isolate and resolve the issue so you can get connected using the Personal Hotspot.
Cheers!
