I had the same problem last week.

@Fae  Suggest the TL unit managing the network tell us the IP Address of the controller instead of just this gateway is being managed....

Thanks for listening

@canopus 

The Omada Controller Software is an application on the PC, to log in the controller software, basically we just need to double click on the software icon or use “localhost:8088” or “localhost:8043” to the address bar. 

The localhost IP address is the IP of the computer that installing the software. 

Another piece of advice is to use Cloud Access to log in the controller software, even the IP of the host PC is changing, you can also visit the controller on the cloud website.

https://omada.tplinkcloud.com/login#controller