Error in production mode "Things don't appear to be working at the moment. Please try again later."

[born2trading]

The payment was working fine in sandbox mode. I started getting following error after changing it to production mode:

Things don't appear to be working at the moment. Please try again later.

The website is developed in Codeigniter. The paypal account type is personal. 

https://born2trading.com/

You can see subscription module in user panel. Then you can try any plan to see the error. 

Thanks in advance for all help from the community.