We have found 2 possible solutions to your problem.
Before you start this troubleshooting guide you need to check one important thing:
Why do we ask this question?
It's important to find out if you can access the internet by loading a web page in the browser on your phone. If you can't access the internet, you need to solve this problem. By solving this problem you'll most likely solve your problem with using your phone as a Wi-Fi hotspot.