Payment Gateway API not working

I am using Payment Gateway API for my online services but when i run API page its shows error This page isn"t working example.com is currently unable to handle this request. HTTP ERROR 500 Please tell me why its happen with API I have another server from godaddy and there i have access cpanel version 78.0.27 My API (Payment Gateway) working fine Please tell me which version cpanel is best that support all third party API and other application and please upgrade my cpanel with best version of cpanel