If your iPhone Personal Hotspot is not working, then try out these several fixes to get things rolling again.
Get Back Online Using Your iPhone Personal Hotspot Using These Fixes
There's a chance that your iPhone might have given up the ghost if you are trying to set up a Personal Hotspot for your notebook or any other device. After all, the underlying software is bound to stub its toe on a table occasionally, but don't panic, we will help you fix things right away using several methods that are outlined below.
Start with the Obvious - Bluetooth & WiFi
Personal Hotspot requires your iPhone's Bluetooth and WiFi radios enabled no matter what. In order to do so, bring up Control Center by swiping up on the display and then enable the WiFi and Bluetooth radios. Those are the second and third toggle switches from the left in the top-most row of icons.
Restart Your iPhone
Power down your iPhone and back up again. If that didn't work, force reset your iPhone. If you have an iPhone 7 or iPhone 7 Plus hold down the Power + Volume Down keys for a few seconds till you see the Apple logo boot screen and let go. If you have any other iPhone then press the Power + Home button together for a few seconds till you boot back up.
Do You Even Have a Working Data Plan?
Personal Hotspot is absolutely useless if you don't have cellular data enabled or don't have a proper data plan at hand. In order to enable cellular data, navigate to Settings > Cellular > Cellular Data. If the toggle switch is enabled and still nothing is working then it's best to call up your carrier and ask them if you have data enabled along with a tethering plan.
Check Your APN Settings
Usually, carriers automatically set the data access point for you over the air. But you can manually set it up as well by going to Settings > Cellular > Cellular Data Options > Cellular Data Network. If this page is completely empty, then ask your carrier to send the APN settings to you, otherwise source them down for your carrier using a search engine.
Check Your Network Coverage
If you have a measly one bar of cellular reception, it's highly likely Internet would not work. Try changing your position a little to get better signals on your iPhone.
Reset Network Settings
Botched network settings can lead to a bad experience as well. Navigate to Settings > General > Reset > Reset Network Settings. Keep one thing in mind though: this will delete all network related settings from your iPhone, such as saved WiFi networks and whatnot. Also, this will remove the APN settings for cellular as well, therefore make sure you have the necessary data ready to be inputted again.
Check Your Notebook or Device Which You Are Connecting to Your iPhone
There's a chance there is something wrong with either your notebook, or the device which you are connecting with your iPhone to go online. Start off with a simple restart, then take things up a notch using different diagnostic routines such as installing the latest WiFi drivers and whatnot.
Update Your iPhone to the Latest iOS Release
Old firmware can be buggy at times, so updating to the latest one is the way to go for most people. Follow the guide here on how to update: How to Download iOS Updates Over the Air (OTA) or Using iTunes.
When All Else Fails...
If you have given up completely and Personal Hotspot is still not working, then take a backup of everything using iTunes or iCloud and restore fresh using iTunes.
Check out the following tutorial before heading out: