iptables does not start after reboot
Solution 1:
Don't rely on the systemctl status of iptables to determine if it's up. The service simply is a onetime service called at boot to run iptables-restore from /etc/iptables/rules.v4 and /etc/iptables/rules.v6. It's not a persistent services.
You would check via sudo iptables -xvnL or similar commands to make sure that iptables rules have populated.