IE mode - missing shared session or cookies between tabs (IE mode and Edge)

[PZac2440]

I have a two site, say site www.site1.com and www.site2.com.

the way how it works is.

I login into first site using my login username and password. After successful login, the site will open a list of links. On one of the links is the www.site2.com (legacy app). Clicking on this will open the second site in a new tab.

With the IE browser coming to an End soon. we are forced to use Edge and IE mode.

I have set www.site1.com to open in Edge mode and www.site2.com in Edge-IE mode. I have followed the instructions give in https://docs.microsoft.com/en-us/deployedge/edge-ie-mode-sitelist and tried https://docs.microsoft.com/en-us/deployedge/edge-ie-mode-add-guidance-cookieshare#how-cookie-sharing...

It seems there is session is not shared between two mode.

below is my xml settings.

not sure if there is something I am missing here.

<site-list version="1">
<shared-cookie domain=".site1.com" name="cookie1"></shared-cookie>
<shared-cookie host=".site1.com" name="cookie2"></shared-cookie>
<site url="site1.com">
<open-in>None</open-in>
</site>
<site url="site2.com">
<open-in>IE11</open-in>
</site>
</site-list>
I also found out that it works when site1 and site2 are using both Edge mode or both as IE mode or both as IE11. But does not work using Edge mode and then IE mode.

I believe I missed something.

[#2]

@PZac2440 Hello!  Thanks for reaching out!  I'm not an expert at this but have you tried making modifications to the "shared-cookie host" portion?  

Based upon the documentation: Cookie sharing from Microsoft Edge to Internet Explorer | Microsoft Docs it says "The host attribute is used for host-only cookies (and a leading dot is an error). " and I see ".site1.com" in your example.  

Also, I'm not sure if it makes a difference but is there a reason the "shared-cookie host" and "shared-cookie domain" portion of your example has the same site ".site1.com"?  

If you are working on deploying MS Edge, have you heard of our FastTrack team (https://www.microsoft.com/en-us/fasttrack/microsoft-365/microsoft-edge)? They can help with configuring MS Edge for your organization and provide guidance with IE mode.  Thanks! 

-Kelly