@Hassegava This sounds familiar and I know it happens when Deco M9 Plus runs firmware version 1.2. Please check firmware version of your Decos. You can find it under Update Deco page in Deco app,...

@Thomas-Deco-M9P Do you run this update tool on Windows computer?

@Thomas-Deco-M9P For the Deco M9 Plus V2, please refer to this link: https://www.tp-link.com/support/download/deco-m9-plus/v2/#Utility I use Microsoft Edge on Windows to download that tool, it...

Earthmatters wrote It's quite frustrating really as i have mentioned it's all working fine on my mobile but will not work on my Windows Laptop and that was the main reason in wanting the Deco M9 Plus...

@Thomas-Deco-M9P To update M9 Plus firmware 1.2 see this document: How to Update the Firmware of Deco Follow Method 3 from it.

@Angstzaaier Just to note, I can access M9 Plus Web interface using Microsoft Edge on Windows. You have quite unusual issue. I don't work for TP-Link, but if I did, that would be my line of thought...