Win11 won't auto connect to Wi-Fi when wired is unplugged

Our issue was newly upgraded (or fresh built) Windows 11 laptops would not connect automatically to the Wi-Fi network when the ethernet cable was unplugged, something our Windows 10 laptops were doing successfully. 

A Win10 laptop would be unplugged from either the docking station or network cable (or network cable from the docking station) and the Wi-Fi card would connect to our Wi-Fi network within a few seconds. On our Win11 laptops, the same action of removing the wired connection would result in the laptop not connecting, just displaying a Wi-Fi symbol with a line through it. 

Manually select a Wi-Fi network and the Win11 laptop would connect. But that's tiresome for the users.

Win11 was fully patched (up to October 2024), HP laptop drivers were updated etc etc, no improvements. Nothing in the event logs to indicate an issue. 

After looking into the applied Group Policies, I narrowed it to the one setting that was the cause. We run the latest CIS Level 1 policy suites to lock down our laptops and due to some customisation of the policies to allow our laptops to cast screens to meeting room TV's, the below setting was changed from the recommended Enabled to Disabled as it blocked this functionality:

Computer Configuration/Administrative Templates/Network/Windows Connection Manager/Prohibit connection to non-domain networks when connected to domain authenticated network

In Win10, this allowed our devices to connect to screens and had no other impact. This same setting of Disabled on Win11 causes our issues above.

Removing the setting (or setting it to Not Configured) from the CIS GPO resolved the issue for us. You can read the explainer here but the interesting part is: If this policy setting is not configured or is disabled, computers are allowed to connect simultaneously to both domain and non-domain networks.

Obviously that is not the case in Windows 11. Hope it helps someone.