Snippet to add extra cost per package to the WooCommerce UPS rate. WooCommerce UPS Shipping Plugin with Print Label - https://www.pluginhive.com/product/woocommerce-ups-shipping-plugin-with-print-label/

functions.php

/**
 * Snippet to add extra cost per package to the Woocommerce UPS rate.
 * Created at : 12 July 2018
 * Updated at : 12 July 2018
 * PluginHive Plugins : https://www.pluginhive.com/plugins/
 * Gist Link : https://gist.github.com/xadapter/5a6404c130dbc61883bda20c392933a4
 */
add_filter( 'wf_ups_rate', function( $response ) {

	$cost_to_add_per_package 	= 10;		// Add fixed cost to shipping rate per package


	$total_received_rate_count 	= count($response->RatedShipment);
	$count = 0;
	foreach( $response->RatedShipment as $key => $ratedshipment ) {
		if( ! empty($response->RatedShipment[$count]) ) {
			$package_count 		= count($ratedshipment->RatedPackage);
			$cost_to_be_added 	= $package_count * $cost_to_add_per_package;
			// Negotiated rates
			if( ! empty($ratedshipment->NegotiatedRates->NetSummaryCharges->GrandTotal->MonetaryValue) ) {
				// Negotiated rate with taxes
				if( ! empty($response->RatedShipment[$count]->NegotiatedRates->NetSummaryCharges->TotalChargesWithTaxes->MonetaryValue) ) {
					$response->RatedShipment[$count]->NegotiatedRates->NetSummaryCharges->TotalChargesWithTaxes->MonetaryValue += $cost_to_be_added;
				}
				else{
					$response->RatedShipment[$count]->NegotiatedRates->NetSummaryCharges->GrandTotal->MonetaryValue += $cost_to_be_added;
				}
			}
			// Normal rate
			else {
				$response->RatedShipment[$count]->TotalCharges->MonetaryValue += $cost_to_be_added;
			}
		}
		$count++;
	}

	return $response;
});

not working