Using Custom Post Meta Values in Shortcode

You cannot print an array directly. The most basic return value you could use is var_export( $meta_values, TRUE );.

This will create a text representation of the value.

Probably better is a little walker like

$output="";

foreach( $meta_values as $key => $value )
    $output .= "$key = " . esc_html( end( $value ) ) . '<br />';

return $output;