Unable to open port on VPS. Firewall problems

Hello, I have VPS server with Ubuntu 18.04 and I am unable to connect to it via port 4200, where I have my application. I tried many things, ufw on ubuntu, setting up 4200 in 'IP' firewall section in OVH dashboard. Also, I disabled OVH firewall and ufw on ubuntu but the result is the same.
Can anyone help?

Thanks :slight_smile: