Fixing iOS HotSpot after iOS 11 update

Turn off your iPhone X/8/7/6s/6 and turn it on again
Before you try the below fixes, a simple way to fix the iOS 11 or iOS 11.1 personal spot missing issue is restarting your iPhone. Some minor iOS system problems can be fixed by a simple restart.
Turn on & Then Turn off Airplane Mode
One of the reasons for iPhone hotspot not working in iOS 11 may be a problem in the data connection. You need to turn on and off Airplane Mode in your iPhone to have a test. To do that, go to the "Control Center" by swiping up the screen from the bottom. Now, look for "Airplane" icon and toggle it on. Wait for a couple of seconds and then turn in off by toggling again. Your cellular network will probably connect again making personal hotspot active ultimately.
Check with Your Carrier & Enable Cellular Data Plan
The primary thing you should have known about is whether you have power to use personal hotspot enabled by your carrier. Putting it simply, you need to contact your carrier in order to verify that the personal hotspot on your iPhone is enabled on the cellular data plan or not. Chances are that your carrier is restricting you from using personal hotspot on the cellular data plan. Therefore, contact your carrier and enable cellular data plan to use personal hotspot feature smoothly.
Check Cellular/Mobile Data settings on iPhone
Make sure you have turned on Cellular/Mobile Data as well as personal hotspot on your iPhone.
To enable Cellular data: Go to Settings > Cellular/Mobile Data > Turn it on > Choose Cellular/Mobile Data Options > Voice & Data > Turn on 3G or 4G. 
Or you can try turning off Cellular or Mobile Data and wait for a few seconds and then turn it on to check if the problem solved.
Update your personal hotspot APN on iPhone
  1. Go to Settings > Cellular/Mobile Data > Mobile Data Options.
  2. Choose Cellular/Mobile Data Networks > Scroll down the screen till you appear Personal Hotspot section.
  3. Enter Same APN as on your cellular data APN.
  4. Once the APN has been updated, switch your phone back to 4G.
Reset Network Settings on iPhone in iOS 11/11.1
  1. Reset network settings on iPhone can help some issues with network that may cause the personal hotspot not working on iOS 11/11.1. Remember this will erase the Wi-Fi passwords, VPN and APN settings and set them to factory defaults.
  2. Go to Settings > General > Reset > Reset Network Settings > Enter your passcode.
Check Your Phone Name
Every iPhone has a phone name, and if you changed the name you may not find the hotspot of your iPhone. To see your phone name: Go to Settings > General > About > Name.

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