Restrict the user to checkout more than one services

restrict_cart_quantity.php

<?php
function restrict_cart_quantity( $item ) {
	$cart_items = edd_get_cart_contents();

	if ( ! empty( $cart_items ) ) {
		foreach ( $cart_items as $cart_item ) {
			$product_type = get_post_meta( $cart_item['id'], '_edd_product_type', true );

			if ( 'service' === $product_type ) {
				edd_set_error( 'edd_one_product_limit', __( 'You can only add one service product to the cart.', 'your-textdomain' ) );

				// Optionally, redirect to the checkout page
				// wp_safe_redirect( edd_get_checkout_uri() );

				// Clear the added item
				$item = '';

				// Exit the loop, assuming you want to restrict to one service product
				break;
			}
		}
	}

	return $item;
}
add_filter( 'edd_add_to_cart_item', 'restrict_cart_quantity', 10, 2 );
?>