@HamxaJutt 

Hi, thanks for posting on TP-Link Community.  

1. For EasyMesh network, we are unable to access the web interface of satellite devices.

Currently, the guest network of the main router will not be synchronized to satellite devices because the satellite devices include router, extenders etc. and extenders don't support guest network at all. We've reported to senior engineers to evaluate if it is possible to synchronize guest network settings when the satellite device is also a router.

2. For Ethernet backhaul issue, what is the hardware and firmware version of both routers? Please note that both of them need to support Ethernet backhaul and make sure it is LAN port of C64 connected to WAN port of C80.

If the problem still exists, please try a different Ethernet cable, also try to unplug the cable from C80 and plug it into a wired computer to see if the Ethernet connection works fine.