Adding XT8 to Mesh with ethernet = blue led

[pvanosta]

I have a few ethernet jacks throughout my home (2 on the ground floor, 2 on the first floor). I have a Mesh of XT8's dotted around the house. The two which are on the ground floor, are connected to the ethernet LAN and ultimately via a switch to a Fiber modem.
I have individually tested the ether ports by walking around with a laptop and connecting it directly to each ethernet port. I have 1GB down and 1GB up on every port in this way (limitation of the laptop).

I have added an XT8 to the mesh by putting it next to the master and connecting the WAN port to the switch. All is well. White led => good to go.
I take it upstairs and plug it into the ethernet port there (which I already know gets GB signal) and power it up. Blinking blue LED.

Side note: I still get the speed benefit in that room, both via wifi and via ethernet to one of the LAN ports. But in the mesh it remains invisible / not connected.

What am I missing / doing wrong?

[jzchen]

I'm honestly not sure what is happening.  But I suggest you try deleting it from AiMesh, hard/factory resetting it.  Place it upstairs and connect it via Ethernet, then try adding it as an AiMesh node.  I find 90+% of the time this works, and you don't have to move the node as it's already where you want it.

[pvanosta]

Just tried that. Didn't work. Got the fast blinking blue led and could not find the node to add to the mesh. Unplugged ethernet and it rejoined the mesh.

[jzchen]

If unplugging the Ethernet caused it to rejoin the mesh it was still registered as an node?/unsuccessfully removed from the Mesh/not hard reset:

https://www.asus.com/us/support/faq/1046973/

[pvanosta]

Thank you, will try that next. Good catch.