Adopt Lite8 POE

I have ~8 Ubiquiti devices (switches and access points) and was able to adopt all of them with no trouble. I want to add a POE 8 Lite but it will not be found by the controller (6.4.54). I tried to connect it in different places in the network (to different ports of the Switch 24 POW that serves as my backbone) but the controller won't find it. I reset it at least 5 times via the hardware switch. It has an IP adress and I can telnet into it. Set-Adopt does not work either. What is the problem here? Where the red circle in the drawing is I have installed a Lite 5 that I wanted to replace by the Lite 8 POE.