Rest API failes to login when tried with Postman

I used this link http://localhost:8000/api/do_login? but it failed. Although when i freshly did it,it was working fine but later i started getting this error .The error was

{
"status": "unauthorized",
"message": "invalid credentials"
}

I used ngrok after that but its still same

 public function login(Request $request)
 {

$validator = Validator::make($request->all(), [
    'username' => 'required|email|exists:customers,email', 
    'password' => 'required'
]);

if($validator->fails())
    return response()->json([
        'status' => 'error',
        'message' => $validator->getMessageBag()->first()
    ], 422);

$customer = customer::where('email', $request->email)->first();

if($customer and Hash::check($request->password, $customer->password))  {
    //authentication successful   
    $customer->access_token = $customer->createToken('login')->accessToken;

    return response()->json([
        'status' => 'success',
        'message' => 'login successful',
        'data' => $customer
    ]);

}else {
    //invalid credentials
    return response()->json([
        'status' => 'unauthorized',
        'message' => 'invalid credentials'
    ], 401);
}



   if( Auth::attempt(['email'=>$request->email, 'password'=>$request->password]) ) {
    $user = Auth::user();

    $token = $user->createToken($user->email.'-'.now());

    return response()->json([
        'token' => $token->accessToken
    ]);
  }
  }

via Chebli Mohamed