Increase WooCommerce Variation Handling Capacity (AJAX- Front End)

/* Increase Woo Variation Handling Capacity (AJAX- Front End) */
function wpflt_woo_ajax_variation_mod( $qty, $product ) {
    return 300;
}       
add_filter( 'woocommerce_ajax_variation_threshold', 'wpflt_woo_ajax_variation_mod', 10, 2 );

By default, WooCommerce can handle only 50 variations per product. More number of variations can be enabled through this code.

However, the front end of the site also loads the default value (50). You should also increase the variation limit, if you have modified the variation limit.