I am using warp which is also known as 1.1.1.1 vpn from cloudflare. My operating system is Ubuntu 20.0. After trials and errors I came to realize the set of commands I need to execute if the vpn is not working or the network is simply not connected.

First you need to disconnect from warp

sudo warp-cli disconnect

Then check your internet connection, it should be working.

Then you need to register before you connect.

sudo warp-cli register

Only after that you can connect to the server.

sudo warp-cli connect

One thing to take note is that if you are using other VPN connection, you need to disable the warp's wifi connection as follows.

sudo warp-cli disable wifi