use of wpdb, I cannot use $wpdb to reach my custom sql table

Hi expert,

I have been trying to use $wpdb in my custom page template, I can get the SQL query run and get the result when i search data in the default wordpress table, but it doesn't show result when i search data in the table i create myself in phpmyadmin, my own table also in the same wordpress database. below is my code.

<?php
$user_count = $wpdb->get_var( "SELECT COUNT(*) FROM $wpdb->trytable" );
echo "<p>User count is {$user_count}</p>";
?>

experts please help my out of this, thank you so much

Ray