Suddenly stopped getting Internet on AX-6000 5G WiFi network

[galapogos]

Hi,
My main desktop (Windows 11 with an Intel AX200 WiFi card) stopped getting Internet on my ASUS ROG GT-AX6000 (firmware version 3.0.0.6.102_34791) 5GHz network yesterday. Here are the facts/symptoms:

• I get Internet on 2.4GHz, and also on another upstream ASUS RT-AC2600 router (both 2.4/5G).
• Windows shows "Secured, no internet" when I connect to the AX6000's 5G wifi, and when I run ipconfig, my Wireless LAN adapter Wi-Fi IP is 169.254.169.61 rather than 10.10.50.x which is my router's subnet. I'm also unable to load the AX6000 admin page when connected to its 5G connection.
• Other devices (laptops/mobile devices) can get Internet over the 5GHz connection.
• I've rebooted both my desktop and the GT-AX6000 router, but still no Internet.
• I've not changed any router settings nor updated the firmware recently.
• There's nothing strange in device manager. No exclamation marks/etc.
• There were a few Windows updates installed yesterday that coincides with the problem (KB5040442, KB5039895, KB5002620, KB5041080, KB5002621), not sure if this could be the culprit.
• I've updated the Intel WiFi drivers from 22.x (released 2023) to the latest 23.60.0/23.60.1 for BT/WiFi but still get the same problem

Any idea why this may be?

Mystery solved. It's a slightly loose antenna.