in my experience the link light only indicates that there is an electrical connection between two Ethernet devices. The link light, however, does not give an indication about whether a device has either a static IP address or received an IP address from a DHCP server. In other words when I connect my POESP32 to a switch where the switch has no further connections (and therefore there is no DHCP server) the link light lights up, but check Ethernet connection returns false. This leads me to think that check Ethernet connection also checks for an IP address and not only for a link.

I suggest you try to connect your POESP32, as a test, to your router directly and / or check on your router whether the POESP32 is listed in its DHCP lease list and has received an IP address.

Note: if you are in a corporate network environment it is possible that the network administrator has setup port security which means an Ethernet device can only participate in that network after it has been whitelisted by said network administrator.

Regarding documentation - I assume you've seen this page?

Thanks
Felix

sorry, I don't have any additional documentation or sample code.

That said, in my tests check Ethernet connection only is true if POESP32 has received an IP address via DHCP. Maybe check you Ethernet cable and/or make sure POESP32 is connected to a network with an active DHCP server.

Thanks
Felix