Hi!
There are many reasons why this might happen, but here are some solutions you might try:
1) Check the usage of personal hotspot data on iPhone. It will give you a detailed breakdown of the data consumed by each connected device. You may have limited monthly data to consume from your carrier. You can control the use of personal hotspot data from the Settings > Mobile Data menu. Find your personal hotspot from the Mobile Data menu and check your device for failure. If necessary, subscribe to an additional data plan from your local carrier.
2) Disable power saving mode from Settings or Control Center to save battery.
If you need to connect the hotspot to your Windows 10 PC, try these steps:
1) Disable power saving mode on your Windows 10 PC.
2) Update network adapter drivers on your Windows 10 PC.
3) Disable the firewall on your Windows 10 PC.
4) Reset network settings on your Windows 10 PC.
5) Update the version of Windows 10.
To update network adapter drivers on Windows 10, you need to open Device Manager. Here’s how to do it:
1) Press the Windows key + X on the keyboard.
2) Select Device Manager.
3) Expand the Network Adapters category.
4) Right-click the network adapter you want to update and select Update driver.
5) Select Automatically search for an updated driver.
6) Select Update driver.
If the problem persists, contact Apple Support.
I hope I helped you!