Payment to this merchant is not allowed (invalid clientid)

I integrated Paypal in my android app in sandbox mode and everything worked perfectly fine. Now I switched to live mode and changed the client ID in my app as well.

Now this error is displayed when I tried to make a test purchase:

"Payment to this merchant is not allowed (invalid clientid)"

I don't know what to do. I changed the client id in every place from the sandbox id to the live id.

My class where Paypal is initialized when click on a button:

public class EssenActivity extends AppCompatActivity {

  private static final String TAG = "Log Essen Activity";
  private String kochuiD, preis, preis_ohne_euro, AnfragePortionenS, ungefahreAnkunftS, preisRe;
  private EditText anzahlPortionen;
  private TextView ungefähreAnkunft;
  private Button essenBesätigenBtn;
  private FirebaseFirestore firebaseFirestore;
  private TextView preisRechner;
  private FirebaseAuth mAuth;
  public static final int PAYPAL_REQUEST_CODE = 7171;
  private static PayPalConfiguration config = new PayPalConfiguration()
        .environment(PayPalConfiguration.ENVIRONMENT_SANDBOX)
        .clientId(Config.PAYPAL_CLIENT_ID);
  private String amount, amountOhneEuro;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_essen);


    essenBesätigenBtn = findViewById(R.id.essenBestätigen);
    essenBesätigenBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
           processPayment();
        }
    }
  }


  private void processPayment() {
    amount = preisRechner.getText().toString();
    amountOhneEuro = amount.replace("€", "");
    PayPalPayment payPalPayment = new PayPalPayment(new BigDecimal(String.valueOf(amountOhneEuro)), "EUR",
            "Bezahle das Essen", PayPalPayment.PAYMENT_INTENT_SALE);
    Intent intent = new Intent(EssenActivity.this, PaymentActivity.class);
    intent.putExtra(PayPalService.EXTRA_PAYPAL_CONFIGURATION, config);
    intent.putExtra(PaymentActivity.EXTRA_PAYMENT, payPalPayment);
    startActivityForResult(intent, PAYPAL_REQUEST_CODE);
  }

  @Override
  //
  public void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
    if (requestCode == PAYPAL_REQUEST_CODE) {
        if (resultCode == RESULT_OK) {
            PaymentConfirmation confirmation = data.getParcelableExtra(PaymentActivity.EXTRA_RESULT_CONFIRMATION);
            if (confirmation != null) {
                try {
                    String paymentDetails = confirmation.toJSONObject().toString(4);
                    startActivity(new Intent(EssenActivity.this, PaymentDetails.class)
                            .putExtra("PaymentDetails", paymentDetails)
                            .putExtra("PaymentAmount", amountOhneEuro)
                            .putExtra("Koch Uid", kochuiD)
                    );
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }

        } else if (resultCode == Activity.RESULT_CANCELED) {
            Log.d(TAG, "onActivityResult: wurde gecancelt");
        }
    } else if (resultCode == PaymentActivity.RESULT_EXTRAS_INVALID)
        Toast.makeText(EssenActivity.this, "Ungültig", Toast.LENGTH_SHORT).show();

  }

  @Override
  public void onDestroy() {
    EssenActivity.this.stopService(new Intent(EssenActivity.this, PayPalService.class));
    super.onDestroy();
  }
}

My Config class:

public class Config {
  public static final String PAYPAL_CLIENT_ID ="MY CLIENT ID";
}

My Paymentdetails class:

public class PaymentDetails extends AppCompatActivity {

  private static final String TAG = "PAYMENT";
  private TextView txtid, txtAmount, txtStatus;
  private FirebaseFirestore firebaseFirestore;
  private FirebaseAuth mAuth;
  private DocumentReference docIdRef;
  private String kochUid;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_payment_details);

    txtid = findViewById(R.id.txtId);
    txtAmount = findViewById(R.id.txtAmount);
    txtStatus = findViewById(R.id.txtStatus);

    Intent intent = getIntent();

    try {
        JSONObject jsonObject = new JSONObject(intent.getStringExtra("PaymentDetails"));
        showDetails(jsonObject.getJSONObject("response"), intent.getStringExtra("PaymentAmount"));

    } catch (JSONException e) {
        e.printStackTrace();
    }
  }

  private void showDetails(JSONObject response, String paymentAmount) {
    try {

        firebaseFirestore = FirebaseFirestore.getInstance();
        mAuth = FirebaseAuth.getInstance();
        String uid = mAuth.getCurrentUser().getUid();

        if (response.getString("state").equals("approved")) {
            DocumentReference documentReference = firebaseFirestore.collection("essen_aktiv_anfrage").document(uid);

            Map<String, String> anfrageMap = new HashMap<>();
            anfrageMap.put("Id", response.getString("id"));
            anfrageMap.put("Status", response.getString("state"));
            anfrageMap.put("Betrag", paymentAmount + "€");
            //NEU
            anfrageMap.put("Anfrage User", uid);
            anfrageMap.put("Koch Uid", kochUid);


            documentReference.set(anfrageMap, SetOptions.merge())
                    .addOnSuccessListener(new OnSuccessListener<Void>() {
                        @Override
                        public void onSuccess(Void aVoid) {
                            Intent intent = new Intent(PaymentDetails.this, MainActivity.class);
                            intent.putExtra("Bezahlung war erfolgreich", "approved");
                            Toast.makeText(PaymentDetails.this, "Bezahlung war erfolgreich", Toast.LENGTH_SHORT).show();
                            startActivity(intent);
                        }
                    });
        } else{
            Toast.makeText(PaymentDetails.this, "Bezahlung war nicht erfolgreich", Toast.LENGTH_SHORT).show();
        }

    } catch (JSONException e) {
        e.printStackTrace();
    }
  }
}

Any help is appreciated. Thank you very much.