@LaToyaVdb 

Hi, what your DDNS address is used for, to access the internal server, or log in to the web interface remotely?

By the way, your current firmware is a little old, and please try to update the firmware to be the latest one:

Deco M9Plus_2.0_upgrade_tool_v1.2.0_Windows: https://static.tp-link.com/2021/202103/20210319/M9Plus_2.0_upgrade_tool_v1.2.0_win.zip

And the latest firmware 1.5.3 https://static.tp-link.com/2021/202104/20210416/Deco_M9Plus_V2_1.5.3_210309.zip

Thank you very much.

@TP-Link 

Hi,

I am trying to access the DDNS address from inside my network, not from outside.

Will try to update the firmware, are there any Linux packages?

Thanks,

@LaToyaVdb 

Sorry, only windows and Mac OS;

https://www.tp-link.com/en/support/download/deco-m9-plus/v2/#Utility 

By the way, if inside via DDNS is not working, how about outside from WAN? maybe it is the NAT loopback issue?

Thank you.