Hotspot

Use these steps first

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. On the iPhone or iPad that provides Personal Hotspot, go to Settings > General > Reset, then tap Reset Network Settings.

If Personal Hotspot is not working on your iPhone or iPad (Wi-Fi

The Hotspot is a carrier-specific feature. Contact your carrier, if it is not appearing on your device.

Meanwhile...

Check the following

1. Network coverage and stability
2. Data Balance
3. On your windows (See if WiFi Auto Joins is enabled)
4. Also, check if you have any stronger WiFi signal around your computer.

The hotspot, VoiceMail (Visual or Normal) all are Carrier Specific features. Contact your Carrier (Cellular Service Provider), the agency that issued the SIM / eSIM to you.