I can't use my phone as a Wi-Fi hotspot
Check the password for the Wi-Fi hotspot on your phone and key in the correct password on the other device.
Can you use the phone's internet connection?
It's important to find out if you can use the phone's internet connection. If you can't use the phone's internet connection, you need to solve this problem first. When the problem is solved, you will most likely also be able to use your phone as a Wi-Fi hotspot.