Firebase Phone Auth suddenly don't works. onCodeSent triggered but no SMS received

UPDATE: Suddenly I tried to attempt this time and it suddenly works without changing any codes on my application and firebase console. I don't know why/how can someone explain? Does anyone know how to prevent this issue?

• this is my verification code history https://i.sstatic.net/U2vMB.jpg

ORIGINAL POST: The onCodeSent is triggered but can't receive any SMS code. It happened to me last time but it turns fine after a day. But last night I can't receive any SMS again without any changes from my android studio codes and firebase in regards to phone authentication. It is the same thing that happened the last time. And earlier as I woke up around 7:00 AM, I can receive an SMS code but then again I tried testing it out again at around 12:00 PM I can't receive any SMS again. I'm not sure what is the problem here. I need an answer as soon as possible because I need my project to be presented on defense next week. Thank you

Also tested on another device from another location. It does not receive any SMS too. Also tried my old project application which is working/receiving SMS but has the same issue.

Firebase Console:

• Phone provider is enabled
• SHA-1 and SHA-256 were applied
• Phone number for testing is empty

Android Studio:

• Connected to firebase project
• No code changes in regards to phone auth
• onCodeSent is triggered but can't receive any SMS code
• Correct number was provided
• Web API Key from firebase console was applied to (curent_key: "key") google-services.json

• Also tried to clean and rebuild the project.

sometimes I receive an SMS code, and not sometime. Toast from onCodeSent was showing. I also try to reveal the token and verificationId and it was not null.

private void sendVerificationCode(String contactNumber) {
        PhoneAuthOptions options =
                PhoneAuthOptions.newBuilder(mAuth)
                        .setPhoneNumber(contactNumber)       // Phone number to verify
                        .setTimeout(60L, TimeUnit.SECONDS) // Timeout and unit
                        .setActivity(this)                 // Activity (for callback binding)
                        .setCallbacks(new PhoneAuthProvider.OnVerificationStateChangedCallbacks() {
                            @Override
                            public void onVerificationCompleted(PhoneAuthCredential credential) {
                                signInWithPhoneAuthCredential(credential);
                                loading.dismiss();
                            }

                            @Override
                            public void onVerificationFailed(FirebaseException e) {
                                Toast.makeText(getApplicationContext(), e.getMessage(), Toast.LENGTH_LONG).show();
                                loading.dismiss();
                            }

                            @Override
                            public void onCodeSent(@NonNull String verificationId,
                                                   @NonNull PhoneAuthProvider.ForceResendingToken token) {
                                verificationDialog(contactNumber);
                                verificationCode = verificationId;
                                loading.dismiss();
                                Toast.makeText(getApplicationContext(), "Verification code sent to " + contactNumber, Toast.LENGTH_LONG).show();
                            }
                        })          // OnVerificationStateChangedCallbacks
                        .build();
        PhoneAuthProvider.verifyPhoneNumber(options);
    }

80% - So this is the answer to my question. Bye