See if post #155 in https://community.tp-link.com/en/home/forum/topic/154561?page=15 is of any help

@BertB I have something very similar working Isp router >> main m9+ >> 4m CAT6 >> TP-LINK Switch >> 20m CAT6 >> second M9+ This is all inside the same house though. Works fine.

@kaja69 I have Deco M9+ as well, the upgrade in my case was very easy, it took 2 steps of 3 minutes. I am also on 1.4.2 firmware I have fiber 500/500, I use the Deco in router mode (my ISP router is...

@toecheese Yes, upgrade to firmware 1.4.x using the upgrade tool mentioned in this forum. I just did it for my M9+ V2 set.

Hi, I just took the plunge and upgraded my set of 3 Deco M9+ V2 from firmware 1.2 to 1.4.0 using the Windows 10 upgrade tool, and then upgraded further to firmware 1.4.2 using the Deco App on my...

@TP-Link_Deco Thank you for the confirmation.