RT-AC66U Multiple-NAT environment and DDNS service cannot work

[heart_dragon]

Hi guys,
I have a Asus RT-AC66U router connected to a router H64ODW (GPON). When I set WAN - DDNS (DDNS client from asus) to use AiDisk from my device. There is problems with my wan ip...

"The wireless router currently uses a private WAN IP address.
This router may be in the multiple-NAT environment and DDNS service cannot work in this environment.".

This is my router setting (H64ODW & AC66U):

Master Router: H64ODW

LAN Connection Information
DHCP Server Enable
IP Address 192.168.1.111
Subnet Mask 255.255.255.0

Internet Connection Information
LAN Connection Information
Interface WAN
IP Allocation SchemePPPoE (Auth: PAP)
IP Address 115.90.156.75
Subnet Mask 255.255.255.255

Asus Router (RT-AC66U)

Wan connection type: Automatic IP
Wan DNS Setting
Connect to DNS Server automatically: yes

WAN Connection Type
Enable WAN Yes
Enable NAT Yes
Enable UPnP Yes

Before there I can use this feature, but now cannot use this function. Please help me how can to fix this problem step by step and can use DDNS client to connect my device through internet.

Any help will be greatly appreciated!

Thanks.

 

[heart_dragon]

somebody please help me 🙁.....