How to resolve "Couldn't execute query"

Once I confirm to work 'petcatalog.php' in the local development envirnoment, I uploaded database and files to the site.

Below are the site folders and files
gosuhdang - site name
mysql_68691_petcatalog database folder
petcolor.ibd
petcolor
pettype.ibd
pettype
etc
img folder
petcatalog.php

Below is a simple script to validate the mySQL connection. It works fine.

$host = "xxx";
$user = "xxx";
$passwd = "xxx";
$dbname = "mysql_68691_petcatalog";

<?php
if (@mysql_connect("host", "user", "passwd")) {
echo "OK - connected to MySQL";
} else {
echo "NOK";
}
?>

mysqli_connect is OK without "couldn't connect to server".
$cxn = mysqli_connect($host,$user,$passwd,$dbname)
or die ("couldn't connect to server");

However, I got "Couldn't execute query".
$query = "SELECT * FROM pettype ORDER BY pettype";
$result = mysqli_query($cxn,$query)
or die ("Couldn't execute query.");

Can you help me which ones went wrong??