Firebase signInWithPopup() giving typeError while signInWithRedirect() is working

i am using the following simple code, which worked for some days and is now not working -

function signIn() {
   // Sign into Firebase using popup auth & Google as the identity provider.
   var provider = new firebase.auth.GoogleAuthProvider();
   firebase.auth().signInWithPopup(provider);
}


document.getElementById("signin").onclick = signIn;

it is giving error -

Uncaught TypeError: e.open is not a function
    at Mt (firebase-auth.js:sourcemap:1)
    at ii (firebase-auth.js:sourcemap:1)
    at zh.t.Xc (firebase-auth.js:sourcemap:1)
    at zh.i [as signInWithPopup] (firebase-auth.js:sourcemap:1)
    at HTMLButtonElement.signIn (sign-in.js:4)

also when i change the signInWithPopup with signInWithRedirect, it is working. I don't know where the problem is? I am using following links in head of index.html -

    <script src="https://apis.google.com/js/api:client.js"></script>

    <!-- update the version number as needed -->
    <script defer src="/__/firebase/8.6.2/firebase-app.js"></script>
    <!-- include only the Firebase features as you need -->
    <script defer src="/__/firebase/8.6.2/firebase-auth.js"></script>
    <script defer src="/__/firebase/8.6.2/firebase-database.js"></script>
    <script defer src="/__/firebase/8.6.2/firebase-firestore.js"></script>
    <script defer src="/__/firebase/8.6.2/firebase-functions.js"></script>
    <script defer src="/__/firebase/8.6.2/firebase-messaging.js"></script>
    <script defer src="/__/firebase/8.6.2/firebase-storage.js"></script>
    <script defer src="/__/firebase/8.6.2/firebase-analytics.js"></script>
    <script defer src="/__/firebase/8.6.2/firebase-remote-config.js"></script>
    <script defer src="/__/firebase/8.6.2/firebase-performance.js"></script>
    <!-- 
      initialize the SDK after all desired features are loaded, set useEmulator to false
      to avoid connecting the SDK to running emulators.
    -->
    <script defer src="/__/firebase/init.js?useEmulator=true"></script>