Sharepoint online - local intranet site

Hello,

My company would like to use a page from our head offices sharepoint site as our home page (intranet) when they open Edge Chromium (Version 85.0.564.68 (Official build) (64-bit)).

For example:

Head office:

https://ContosoGroup.sharepoint.com

Our divisional page:

https://ContosoGroup.sharepoint.com/sites/Div-landing

The users were getting prompted to enter their U&P at sign in.

So I added:

*.sharepoint.com

To the Local Intranet websites and auto logon with the users U&P via a Zone Mappings GPO.

Now when users logon they can get to head offices website with any prompt (and then our page if they follow the url).

But if they open Edge and and go directly to our page (sites/Div-landing) it propts for credentials:

From what I undertand I dont need to add the untire url to the zone mapping.

I've also tested with trusted zone with the same issue.

Could this be an issue with the page on sharepoint we've made?