MERN/Axios login only works in opera

Question

I'm creating a forum/imageboard project to learn the MERN stack and while testing my web I've found out that my login system only works in opera. This is what my code looks like:

const [user, setUser] = useState({
    name:"",
    password:""
});
const handleChange = e => {
    const {name, value} = e.target;
    setUser ({
        ...user,
        [name]: value
    });
}
const setLoginUser = (loginUser) => {
    sessionStorage.setItem('activeUser', loginUser);
}

const login = () => {
    axios.post("http://localhost:3001/login", user)
    .then(res => {alert(res.data.message);
    setLoginUser(res.data.user);
    navigate("/");
    })
}

This is my backend:

app.post("/login",(req, res) => {
const {email, password} = req.body;
UserModel.findOne({email:email}, (err, user) => {
    if(user){
        if(password === user.password){
            res.json({message: "login succesful", user:user});  
        }else{
            res.json({message: "wrong password or email"})
        }
    }else{
        res.json("not registered");
    }
  });
});

I know sessionStorage is not the best for this but is honestly the only way I managed to do this.