Double check that you're not using a sandbox client for production. I get a different error mixing up credentials (paypal failed to create an order ID) , but it's worth a quick check.
However, I can exactly reproduce what you're seeing if I set the ServiceScriptUrl property in Defaults.cs to http://
public static string ServiceScriptUrl => "http://www.paypal.com/sdk/js";
If you have the source code you should double check that hasn't been edited from https for some reason. If you're using the precompiled binaries then it's something else, and since you get the same behavior with both plugins I'm guessing it's something with your server configuration.PayPal only supports TLS 1.2
. I took the liberty of checking your domain over at SSLLabs.com and it says that your server still supports TLS 1.1, so there is a chance that PayPal's SDK isn't loading over that protocol. You would think it would use the most secure, but who knows. Also, makes sure it's using HTTP/1.1 in your dev console.
If you have access to the server there is a great tool called IIS Crypto that makes disabling TLS 1.0 / 1.1 a breeze, otherwise google how to edit the registry.
I can't guarantee that's the problem, but it's where I would start.