Lightning Out : Uncaught ReferenceError: $A is not defined when user is not logged in

Question

I want to use my LWC'in an External Site (Heroku). For it I use Lightning Out.

I have built a simple Aura Application (in my Sandbox) according to documentation here : Lightning Out Dependencies

<aura:application access="Global"  extends="ltng:outApp" >
    <aura:dependency resource="c:testLWC"/>
</aura:application>

I have implemented the OAuth using JWT auth (based on this great video : Implementing a JWT Server to Server OAuth between Salesforce and Heroku ).
The main method (which connects to Lightning Out) in the Heroku :

let renderLightningOutComponent = (token) => {
    $Lightning.use(
        "c:LightningOutDemo", 
        function() {
            $Lightning.createComponent(
                "c:testLWC", 
                {},
                "testLWC",
                function(cmp) { /* ToDo */}
            );
        },
        "https://{my-domain}.lightning.force.com",
        token
    )
};

-- ERROR --

If my user is NOT logged in Salesforce, I get next errors in JS Console :

And the Network :

It works without the problems if a users is logged in !

So as I understand the $Lightning.use() method fails for some reason when a user is not logged in the Sandbox.
As I see it tries to load some resource as app.css, aura_prod.js etc.

IMPORTANT :
I do NOT have this issue if I try to connect to my Developer org .

Is there is something that I am missing ?

Any help will be appreciated.
Thank you.

Answer 1

The issue is with Enhanced Domains. (https://help.salesforce.com/s/articleView?id=sf.domain_name_enhanced.htm&type=5)

Enabling enhanced domains adds a .sandbox. to the URL, which is causing a few problems with Lightning Out.

I recommend disabling Enhanced Domain in the Sandbox so you can use/test it.

Production and Dev Orgs don't have the .sandbox. part added to the URLs which is why it works correctly there.