Check to see whether Personal Hotspot is turned on. You can look in two different areas. This information may be found by going to Settings->Personal Hotspot or Settings->Cellular-> Personal Hotspot. If you can't discover or activate Personal Hotspot on your device, check with your wireless provider to see if the service is available or enabled on your plan.
Attempt to change your internet connection. If you're currently connected by Wi-Fi, for example, try connecting using Bluetooth or USB instead..
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Restart your iPhone (source) and any other devices that are linked to it.
Check to see if your iPhone and other devices are running the most up-to-date software.
Restart your network. Go to Settings-> General-> Reset-> Reset Network Settings on your iPhone 6s Plus or any device that supports Personal Hotspot. This will reset the network settings and utilise the default network access settings.
