FOX - Currency Switcher Professional for WooCommerce

Plugin site: https://codecanyon.net/item/woocommerce-simple-auctions-wordpress-auctions/6811382

Into file functions.php of the current WordPress theme add next code:

add_filter('woocommerce_simple_auctions_get_current_bid', function ($price, $_this) {

    if (class_exists('WOOCS')) {
        global $WOOCS;
        if ($WOOCS->is_multiple_allowed) {
            $price = $WOOCS->woocs_exchange_value(floatval($price));
        }
    }

    return $price;
}, 20, 2);

add_filter('woocommerce_simple_auctions_get_increase_bid_value', function ($bid, $_this) {
    if (class_exists('WOOCS')) {
        global $WOOCS;
        if ($WOOCS->is_multiple_allowed) {
            $bid = $WOOCS->woocs_exchange_value(floatval($bid));
        }
    }

    return $bid;
}, 30, 2);

add_filter('woocommerce_simple_auctions_place_bid_value', function ($bid, $product_id) {

    if (class_exists('WOOCS')) {
        global $WOOCS;
        if ($WOOCS->is_multiple_allowed) {
            $currencies = $WOOCS->get_currencies();
            $conversion_rate = $currencies[$WOOCS->current_currency]['rate'];
            $bid = $bid / $conversion_rate;
        }
    }

    return $bid;
}, 30, 2);