@Solla-topee Hey,

Thanks for the quick reply.

All of them except the 5ghz are lit up in blue. Sometimes the last right one blinks to red. 

By build number I assume you mean model number? That's RE580D (UN) ver 1.0. I have upgraded the firmware to the latest build available on the tp link website for the UN version: 1.0.0 Build 20171220 Rel. 57215

After setting it up the first time it worked for about an hour. The second time I set it all up using the manual DHCP server settings and it worked for about 30 minutes and then stopped again, returning to this state. When restarting it, it can randomly change between showing it has internet connection or it doesn't, but either time there's no actual internet connection.

Currently the internet is actually working on it despite the Extenders interface saying it is not. This changes randomly without any other changes in the network and at random intervals.

The archer C80 router does not see the RE580D in its list of connected DHCP clients despite it being the one providing wifi and ip address to the extender

I'm not sure what else I can try to fix it.

@Solla-topee interestingly enough, I just got on my pc which is connected by lan wire to the Archer c80 and it didn't have any internet connection because it was getting the ip address and default gateway from the RE580D, even though it is not connected to it in any way other than through the wireless network provided by the C80. Somehow the RE580D is taking over the process of handing out the DHCP for all devices on the network instead of just the ones connected to it