Just bought a new XE75 system and having trouble getting the ethernet backhaul working via a TP Link Unmanaged switch TL-SG1024D

The nodes are all connected to the main unit that is also the Router. The main unit is plugged into the switch and the nodes are plugged into the switch. Without the ethernet cable the nodes have the Green led light. But the moment I plug the ethernet cables in the light blinks Red.

I have a network that looks like the 2nd diagram as shown here in Q2.

https://www.tp-link.com/uk/support/faq/1794/

If I plug the ethernet cable directly from 1 node to another everything works fine. 

If I reset the node and power it on with the ethernet cable plugged into the child nodes from the switch the blue led keeps blinking. If I try and Add a Deco Unit then the app finds the reset Deco child node but then fails when trying to apply the settings.

https://community.tp-link.com/en/home/forum/topic/98849 refers to the exact same problem but my nodes have the latest firmware but are refusing to using the ethernet backhaul via the TP Link unmanaged switch.