Volumio 4G LTE USB dongle + hotspot

Hi, I am trying to create a mobile hotspot from my volumio on a RPI 4 where phones and other devices can connect to to allow everyone to stream spotify music(off grid system). I have a usb dongle that allows for a sim card to be installed that gives the device a wired network connection. The device does send out a hotspot but does not seem to have any connection. could the problem be the dongle or does this configuration just not work?

Update:

The device does seem to have internet connection as i do appear to be logged and being able to update plugins. The device is discoverable via spotify devices on the phone. but connecting to it just gives a “connecting…” status for 5 seconds and then nothing.

Volumio only works on the same subnet as the dongle, If the dongle exposes a hotspot, the mobile devices need to connect to this hotspot.

I just don’t get why you want to go this way, or better what the benefits are dongle vs normal network.

I am building a speaker based around volumio that is supposed to work on a car battery(Off the grid, big boy speaker). It has a raspberry pi 4 and a 7" touchscreen. It should be able to connect to any wifi network when there’s one available but I want to be able to connect phones and stream from Spotify, SoundCloud, YouTube,… on the hotspot it sends out when no wifi network is available. So I would expect it to need a connection to 4G.

Are there any other methods todo this?

I don’t want the system to depend on anyone’s phone so that’s not going to be an option.

I ordered a mifi router from TP-link(U plug in a sim card and it sends out a wifi network) so that will probably work as well. If I just connect the pi and phones to that when nothing else is available.