Problem with Paypal Configuration

[peoplej.com]

PrestaShop1.5.4.1

 

I have been trying to configure Paypal for my website, however both Paypal 1.2.1 & 3.5.5 didn't work after I input everything on the API settings, please help!

 

Errors show as follows:

Paypal 1.2.1

Your Paypal API crendentials are not valid, please double-check their values or contact PayPal.

 

Secure payment

 

 

Our secure payment

 

With SSL

Using Visa/Mastercard/Paypal

 

 

Paypal 3.5.5

 

Internal fatal error 3.5.5

 

Server Error

 

The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator, and inform them of the time the error occurred, and anything you might have done that may have caused the error.

More information about this error may be available in the server error log.