Page template not displaying

This is less of an answer and more of a kind of troubleshooting aid… Add this function to your project (probably functions.php) and then call it from the top of every template file in your theme…

/**
 * Outputs the name of the file as an HTML comment for easy-peesy troubleshooting.
 *
 * @param string $file This function should always be passed the value of __FILE__
 */
function output_file_marker( $file )
{
    // Strip out system path (keeping only site-root-relative path)
    $file = preg_replace( '|' . preg_quote( ABSPATH ) . '|', '', $file );

    // Output an HTML comment with the current template path
    printf( "\n\n<!-- ".__( 'Template file: %s', 'nvLangScope' )." -->\n\n", "https://wordpress.stackexchange.com/".$file );
}

This will help you identify which template file is being loaded by outputting an HTML comment at the start of each template, and can help you solve a lot of weird “wrong template” problems.

Second, try this…

Set your Page Attribute > Template back to Default, then rename your template file according to the page number instead of the slug (you may also want to remove the template name… just in case). For example, if your problem page had a post id of 103, you would name the template file page-103.php

If you want to keep the template as an admin-selectable override template, then use a different naming convention. I use override-description.php when a template should be admin selectable.

Finally, make sure any and all plugins are disabled. Plugins can mess with templates by overriding them… this is particularly true of certain eCommerce packages.