Lightningout not working after successful authentication

[devashishkhandelwal]

Lightning out component not getting loaded after authentication, Authentication is working fine. After calling

$Lightning.use(
         appName,
         function () {
           alert("ready done ");
           _lightningReady = true;
           document.getElementById("lexcontainer").style.display = "";
           if (typeof callback === "function") {
             callback();
           }
         },
         url
       );

We are getting this error

Uncaught SyntaxError: Unexpected token '<', "


<!DOCTYPE "... is not valid JSON
    at JSON.parse (<anonymous>)
    at lightning.out.delegate.js?v=1688973633677:168:43
    at xhr.onreadystatechange (lightning.out.delegate.js?v=1688973633677:137:17)
(anonymous) @ lightning.out.delegate.js?v=1688973633677:168
xhr.onreadystatechange @ lightning.out.delegate.js?v=1688973633677:137
XMLHttpRequest.send (async)
requestApp @ lightning.out.delegate.js?v=1688973633677:151
use @ lightning.out.delegate.js?v=1688973633677:165
script.onload @ lightning.out.js:46
load (async)
loadDelegateScript @ lightning.out.js:43
(anonymous) @ lightning.out.js:53
(anonymous) @ lightning.out.js:78

Pleaes help on this issue. Thanks in advance