My buttons doesn't react when fields are full

When I put the information in the textfields the button just doesn't react when I click it. The data goes to Firebase but it doesn't affect how the app works. My Toast message is working if the textfields are empty(the button reacts), but when they are full nothing on screen happens. When signing up or in, the screen should go to Main Activity but nothings happens. Here is my code:

LoginActivity

class LoginActivity : AppCompatActivity() {
    private lateinit var auth: FirebaseAuth


    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_login)
       auth = Firebase.auth


        var signuplinkbtn = findViewById<Button>(R.id.signup_link_btn)

        signuplinkbtn.setOnClickListener {
            startActivity(
                Intent(
                    this,
                    RegisterActivity::class.java
                )
            )
        }

        val loginButton = findViewById<Button>(R.id.login_btn)

        loginButton.setOnClickListener {
            performLogin()
        }

    }

    private fun performLogin() {
        val email = findViewById<EditText>(R.id.email_login)
        val password = findViewById<EditText>(R.id.password_login)

        if (email.text.isEmpty() || password.text.isEmpty()){
            Toast.makeText(this, "Please, fill all fields", Toast.LENGTH_LONG).show()
            return
        }
        val emailInput = email.text.toString()
        val passwordInput = password.text.toString()

        auth.createUserWithEmailAndPassword(emailInput, passwordInput)
            .addOnCompleteListener(this) { task ->
                if (task.isSuccessful) {
                    // Sign in success, move to Main Activity
                    val intent = Intent(this, MainActivity::class.java)
                    startActivity(intent)

                    Toast.makeText(
                        baseContext,
                        "Success",
                        Toast.LENGTH_SHORT,
                    ).show()

                } else {
                    // If sign in fails, display a message to the user.

                    Toast.makeText(
                        baseContext,
                        "Authentication failed.",
                        Toast.LENGTH_SHORT,
                    ).show()
                }
            }
            .addOnFailureListener {
                Toast.makeText(this, "Error occured", Toast.LENGTH_LONG).show()
            }
    }
}

RegisterActicity:

class RegisterActivity : AppCompatActivity() {
    private lateinit var auth: FirebaseAuth


    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        auth = Firebase.auth

        setContentView(R.layout.activity_register)
        var signinlinkbtn = findViewById<Button>(R.id.signin_link_btn)

        signinlinkbtn.setOnClickListener { startActivity(Intent(this, LoginActivity::class.java)) }

        val registerButton = findViewById<Button>(R.id.signup_btn)
        registerButton.setOnClickListener { performSignUp() }

    }

    private fun performSignUp() {
        val email = findViewById<EditText>(R.id.email_register)
        val password = findViewById<EditText>(R.id.password_register)

        if (email.text.isEmpty() || password.text.isEmpty()){
            Toast.makeText(this, "Please, fill all the fields!", Toast.LENGTH_SHORT).show()
            return
        }

        val inputEmail = email.text.toString()
        val inputPassword = password.text.toString()

        auth.createUserWithEmailAndPassword(inputEmail, inputPassword)
            .addOnCompleteListener(this) { task ->
                if (task.isSuccessful) {
                    // Sign in success, move to Main Activity
                    val intent = Intent(this, MainActivity::class.java)
                    startActivity(intent)

                    Toast.makeText(
                        baseContext,
                        "Success",
                        Toast.LENGTH_SHORT,
                    ).show()

                } else {
                    // If sign in fails, display a message to the user.

                    Toast.makeText(
                        baseContext,
                        "Authentication failed.",
                        Toast.LENGTH_SHORT,
                    ).show()
                }
            }
            .addOnFailureListener {
                Toast.makeText(this, "Error occured", Toast.LENGTH_LONG).show()
            }
    }
}

If someone has any idea what the problem is, I'd be glad to know.

I think you are missing something; in order to log in with Firebase Auth, you need to use signInWithEmailAndPassword and not createUserWithEmailAndPassword, because the latter is used to create users for the first time, that's why it is not working I think.

Modify your code as follows In LoginActivity:

private fun performLogin() {
    val email = findViewById<EditText>(R.id.email_login)
    val password = findViewById<EditText>(R.id.password_login)

    if (email.text.isEmpty() || password.text.isEmpty()) {
        Toast.makeText(this, "Please fill all fields", Toast.LENGTH_LONG).show()
        return
    }
    
    val emailInput = email.text.toString()
    val passwordInput = password.text.toString()

    auth.signInWithEmailAndPassword(emailInput, passwordInput)
        .addOnCompleteListener(this) { task ->
            if (task.isSuccessful) {
                // Sign in success, move to MainActivity
                val intent = Intent(this, MainActivity::class.java)
                startActivity(intent)
                Toast.makeText(baseContext, "Login success", Toast.LENGTH_SHORT).show()
            } else {
                // If sign in fails, display a message to the user.
                Toast.makeText(baseContext, "Authentication failed.", Toast.LENGTH_SHORT).show()
            }
        }
        .addOnFailureListener {
            Toast.makeText(this, "Error occurred", Toast.LENGTH_LONG).show()
        }
}

Hope that will solve the issue 🙏