I am using a React client and a node js server (MERN Stack). The server runs good on my pc but when i try to connect from my mobile phone to the ipv4 of my pc with the correct port I am unable to send requests to the server. I tried to change the proxy of the React app but it doesn't seem to work. Do you know what the problem might be? Thanks.
That could be a network issue if your are trying to access your PC from an external IP (Phone not connected to local network, wifi), for example the PC connected to a router that does not forward external traffic to it.
If you can, try connecting your phone to the same network via wifi and access the local IP:PORT instead of ipv4.