Storing cookie with SameSite option as `Any kind of connection` - google-chrome

Question

Im working on a .NetCore MVC project.
As the title suggests my goal is to store a cookie that will eventually be accessible through an iframe.
In order to achieve that this is what I did -
Startup.cs -
app.UseCookiePolicy(new CookiePolicyOptions
{
MinimumSameSitePolicy = SameSiteMode.None
});
Using the actual CookieOption class -
public void SetCookie(string key, string value, int? expireTime, HttpResponse Response)
{
CookieOptions option = new CookieOptions();
//allow cross-site cookies for iframes
option.SameSite = SameSiteMode.None;
if (expireTime.HasValue)
option.Expires = DateTime.Now.AddMinutes(expireTime.Value);
else
option.Expires = DateTime.Now.AddMilliseconds(10);
Response.Cookies.Append(key, value, option);
}
Doing the above It seems like it doesn't always work as intended.
Iv'e tested lots of browsers both desktop and mobile.
Just found out that sometimes the cookie is stored successfully like so -
Send for:
Any kind of connection
Accessible to script:
Yes
And sometimes on the same exact chrome version just a different computer its stored like so -
Send for:
Same-site connections only
Accessible to script:
Yes
Which basically means it won't be accessible using iframes.
The problem isn't a specific computer issue as I was managed to duplicate the problem on 3 different computers running the same chrome version which works fine on other computers.
The example above was produced using this chrome version (last version):
Version 80.0.3987.149 (Official Build) (64-bit)
Anyone have an idea how can I overcome that ? gotta make sure cookies will always be accessible using an iframe.
Thanks!
Edit - Attempt with Secure and HttpOnly flag
So iv'e adjusted my code to set the HttpOnly and the Secure flags to true.
The computers that usually worked fine had this cookie settings -
Send for
Secure connections only
Accessible to script
No (HttpOnly)
And it works fine with iframe.
The computer which didn't work before had this cookie settings -
Send for
Secure same-site connections only
Accessible to script
No (HttpOnly)
Which obviously didn't work with an iframe...
Just updating of another approach that didn't work.
Edit 2 - Using fiddler to intercept the cookies response:
So using fiddler to read the cookie this is what it looks like -
Set-Cookie: __cfduid={randomvaluehere}; expires=Fri, 24-Apr-20 17:37:48 GMT; path=/; domain=.domain.com; HttpOnly; SameSite=Lax
Set-Cookie: mycookie=mycookievalue; expires=Fri, 24 Apr 2020 17:37:49 GMT; path=/; secure; httponly
So seems like the response is storing a cookie with is SameSite=Lax on the apex of the domain, which I don't care about.
I work on a sub-domain which is the second set-cookie that is shown above.
Looks like SameSite=None isn't explicitly presented, should it? if so why wouldn't it seeing the code above?
Also reminding you that exactly that works fine for other browsers or other computers with the same chrome version.
The sample above is exactly the same on computer where it worked and in one that it wasn't.