支付宝app支付总是提示系统繁忙请稍后再试ALI40247，返回的sub_msg:62009后端用的是php，ios提示4000，...286，ALI40247，怎么解决，后台请求的字符串如下：

分类：HTML5+

alipay_sdk=alipay-sdk-php-20161101&app_id=2017041906811082&biz_content=%7B%22body%22%3A%221%3A1%3AAPP%22%2C%22subject%22%3A+%22App%E6%94%AF%E4%BB%98%22%2C%22out_trade_no%22%3A+%22RC20180502175133286486%22%2C%22timeout_express%22%3A+%2230m%22%2C%22total_amount%22%3A+%220.01%22%2C%22product_code%22%3A%22QUICK_MSECURITY_PAY%22%7D&charset=UTF-8&format=json&method=alipay.trade.app.pay&notify_url=http%3A%2F%2Fddx.yiquwl.com%2Faddons%2Fewei_shopv2%2Fpayment%2Falipay%2Fnotify_app.php&sign_type=RSA2&timestamp=2018-05-02+17%3A51%3A33&version=1.0&sign=jn3mlDvX3z1pV6tYwQ2ZDbGR%2FWnaNZjeHoGXuU%2BozwuNaKA2Gq4%2B%2FghZ7gctVO%2F9xgUVM%2BoVpaweMleRTb1U0k%2FslCL%2FqejK17AmMfdT3DKqjKPEoZn1B0Ytav%2B7%2BHz6R%2BVZ4yRCvIF4gm1MfhTiY8FX5ikNmTsiXbINn7NhOf1bL6SDuJ90tqrTP9LQZZFveHDCiEN1omVjEQeWpQun7PfwJ9ujahS%2B3Z%2B9f1g236%2BIab6jjC%2BghqDIcGMmZzm7EFkjaUbxZ4EG3Vvnn9Q4aUZOVpKnwhnL%2BtnAU40Pdnxn%2FBHI%2BZjXPjcNHcPK3gRgbddWMFPr9puX8zqhH6Jz4Q%3D%3D