The hotspot connection works, but I can't access the internet

I'm a beginner trying to use Linux for the first time.

I installed Ubuntu 22.04 on an assembled desktop that is not connected to the internet.I'm in a situation where I cannot use a wired Ethernet connection.

So, I tried to connect to the internet temporarily via a Bluetooth hotspot.Following the instructions at https://community.kinivo.com/t/how-to-install-btd-500-firmware-for-linux/280, I successfully installed it and confirmed that Bluetooth peripherals are recognized, and it shows as connected when I connect it to my iPhone.However, the internet does not work when I run Firefox.

How can I solve this problem? I ended up using a Bluetooth hotspot because I needed internet access while trying to install wireless WiFi.

I would really appreciate your help.Thanks!