1. Make sure the telnet in Administration > System tab > Telnet is enabled. Or SSH enabled if you prefer SSH.
2. Telnet to your router using Putty tool, login. Make sure putty is tick Telnet. If SSH then SSH ticked.

3. Type in command “nvram show | grep asus_device_list
You will see something similar to this, below AC68U is my wifi SSID, same goes to MAC and router IP.
Make sure you copy yours, not mine. lol

Sample result:
asus_device_list=<3>TENDA>192.168.1.1>D8:65:63:D4:3D:40>0>AC68U>255.255.255.0>1

4. Copy the entire string above except “asus_device_list=” and also replace “TENDA” to “RT-AC68U

Command: nvram set asus_device_list=”< paste the string starting from <3> until 255.255.255.0>1 >”

Sample:
nvram set asus_device_list=”<3>TENDA>192.168.1.1>D8:65:63:D4:3D:40>0>AC68U>255.255.255.0>1″

5. Type in command “nvram show | grep asus_device_list” again to check whether it has the latest changes you made.

6. Next, type in “nvram show | grep odmpid”
You will see it’s showing TENDA

7. Type in nvram set odmpid=RT-AC68U (For this part, after commit & reboot, if you issue “nvram show | grep odmpid” again it will be empty, but it still works. Need other sifu to comment on this part)

8. Type in “nvram show | grep odmpid” to check again.

9. Check your setting with this command, nvram show | grep RT-AC68U
computer_name=RT-AC68U

odmpid=RT-AC68U
asus_device_list=<3>RT-AC68U>192.168.1.1>D8:65:63:D4:3D:40>0>AC68U>255.255.255.0>1

10. Type in nvram commit to to apply.

11. Type in “reboot” and router will reboot. 

12. Download ASUS router app to try

source: https://forum.lowyat.net/index.php?showtopic=4504268&view=findpost&p=90503295