cannot access webmin on Google cloud after it was working

I added webmin rule in Google Cloud Dashboard> VPC Network > firewall rules already. Actually it worked normally many days before. However, today I cannot access webmin.

sudo netstat -anlp | grep :10000

tcp 0 0 0.0.0.0:10000 0.0.0.0:* LISTEN 1288/perl

tcp6 0 0 :::10000 :::* LISTEN 1288/perl

udp 0 0 0.0.0.0:10000 0.0.0.0:* 1288/perl

Use this command and it worked:
sudo iptables -A INPUT -p tcp -m tcp --dport 10000 -j ACCEPT