My app can't send data to Mysql database

Hey guys, we've been making this app to receive 3 data from arduino devices and then storing them to a mysql database. we found out that the app didnt send the data at all and we are at a lost as to what happen. here is our blocks that send the data:

and here is the php code we use:

<?php include 'koneksi.php'; $Username = $_POST['Username']; $Password = $_POST['Password']; $cek_data=mysqli_query($koneksi,"SELECT * FROM pengukuran_air WHERE Username='$Username'and Password='$Password'"); $cek=mysqli_num_rows($cek_data); if($cek > 0){ $row_akun=mysqli_fetch_assoc($cek_data); $_SESSION["akun_id"]=$row_akun['Id']; $Jenis_Air = $_POST['Jenis_Air']; $Tanggal_Pengukuran = $_POST['Tanggal_Pengukuran']; $TDS = $_POST['TDS']; $pH = $_POST['pH']; $Suhu = $_POST['Suhu']; $id = $_SESSION["akun_id"]; $query="INSERT INTO hasil_pengukuran_air SET Jenis_Air='$Jenis_Air',id='$id',Tanggal_Pengukuran='$Tanggal_Pengukuran',pH='$pH',TDS='$TDS',Suhu='$Suhu'"; if(mysqli_query($koneksi, $query)){ echo"Berhasil"; } else { echo"Error: ".$sql. "
" .mysqli_error($koneksi); } mysqli_close($koneksi); } ?>