I did not see any related issue between OpenVPN and Iptables. What is your problem?
I've successfully installed OpenVPN in my company, usually, you have to modify the firewall rule to make it work.
I assume you are using bridging VPN (ie. tun interface).
On the server, enter those command
iptables -I INPUT -i tun0 -j ACCEPT
iptables -I FORWARD -i tun0 -j ACCEPT
iptables -I INPUT -o tun0 -j ACCEPT
iptables -I OUTPUT -i tun0 -j ACCEPT
Do the same on the client.
Those rules just make OpenVPN to work, but they are INSECURE. You should modify these rules into stricter ones.
Hope this may help.
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