Yes, of course (in case you are using nftables and not iptables). Who knows, which other tools have manipulated the settings.
And which server is running on port 3000? Check it with "netstat -tulpen" or "ss -tulpen".
//Add:
There is no server running in Port 3000. That is the reason why the port is closed.
I wiped the OS 3 times wondering what was happenning so no other tools manipulating stuff. only my ignorance of how things works
Thank you again ! will try to install the service first