(Firebase Firestore)TypeError: n.indexOf is not a function

I’m trying to add another field value in a document but firebase returns TypeError: n.indexOf is not a function. Here’s the code:

async function linkLCSN(cor, sn) {
  try {
    await setDoc(doc(db, "cor", cor), {
      sn: sn,
    }, {merge: true});
  } catch(e) {
    console.error(e);
  }
} 

I’ve already succeeded in doing this way but I don’t know why this time it keeps giving me this error. This is the working code:

async function submitToDatabase(name, email, cor, cs, cn, concern) {
    try {
        //Set Datas 
        await setDoc(doc(db, "cor", cor), {
        name: name,
        email: email,
        cor: cor,
        courseSection: cs,
        contactNumber: cn,
        isViewed: false,
        timestamp: serverTimestamp(),
        }, {merge: true});
        const docRef = await addDoc(collection(db, "cor", cor, "concerns"), {
        concernData: concern,
        });
        console.log("Yung betlog nasa:" + docRef.id);
        //Do page changes
        let a = document.querySelector(".concern-main-container");
        let b = document.querySelector(".concern-preview-container");
        a.style.display = "none";
        b.style.display = "block";
    } catch(e) {
        console.error(e);
        //Custom Alert
    }
}