When ever I click on PayPal it show an alert “service Unavailable”

问题

I am using PayPal payment gate way when ever I click on my it shows alert and payment is not successful I have attached a ScreenShot please let me know what I did wrong.

And my response is below

Error: {
category = Application;
errorId = 503;
message = "service unavailable";
severity = Error;

}

来源：https://stackoverflow.com/questions/52809975/when-ever-i-click-on-paypal-it-show-an-alert-service-unavailable