This Error due to internal server error. When PayPal does not receive HTTP 200 success code from server then, PayPal shows this Error Code 500.
Due to HTTP error code, SSL Validation, Network timeout and HTTP error 503, this error occurs in your PayPal. This error also occurs due to your "Unable to connect to the remote server" and problem in your IPN script code.
By opting 3 below steps you able to solve your error code that is (500 PayPal Error Code).
Checkout your checkout your Network again.
Switch off your Wifi and Switch On your WiFI. Now, connect again with you Computer, Laptop or Mobile.
Debug your Connection again, if problem not resolved.
Hope above 3 Steps able to solve your PayPal Error Code 500 and you will able to do your business payment through PayPal.
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