Some problem about openwrt firewall port forward

Hello:
I've met some problem about openwrt firewall port forward.

Openwrt has a public ip address and worked as an openvpn server.
There is a plex server connected to openwrt through openvpn client and surfed the Internet normally(all traffic go through openvpn server) which behind nat.

plex server information:
local ip address: 172.19.68.22
openvpn client ip address: 192.168.8.2

openwrt information:
wan ip: x.x.x.x
br-lan ip address: 10.0.0.1
openvpn server ip address: 192.168.8.1

openwrt has an interface named rovpn belong to firewall zone rovpn.
Here is openwrt firewall zone setting.


Here comes the problem, I set up a firewall port forward rule: wan:32400 -> 192.168.8.2:32400. However it failed.

Specifically:
Suppose the wan interface address is A。
If I run ‘wget 192.168.8.2:32400’ ,the output is ‘connected’.
BUT.
No matter I am inside or outside the openwrt environment, the output of "wget A:32400" is always connetciton refused. :joy: :joy: :joy:
Uh, is there any way to figure out this issue?
Thank you all.