This is a gotcha but be aware sometimes iptables may be active and loaded by default.
Also make sure you don't just disable firewalld but also stop it otherwise it will still block stuff:
systemctl stop firewalld
If the above is not the issue then it is possible iptables is running and blocking stuff too, so you'll need to stop iptables.
So in addition to opening firewalld or disabling it, you would need to disable iptables too:
systemctl stop iptables
systemctl disable iptables