Paypal Api for wordpress theme

[mindonmouse]

I am having Wordpress Dashboard for PayPal Integration with Inputs 

           Paypal Client ID:   

Paypal Client Secret Key:

    Paypal API Username:   XXXXXXXXXXXX

     Paypal API Password:   XXXXXXXXXXXX

     Paypal API Signature:  XXXXXXXXXXXX

Paypal Receiving Email

 :XXXXXXXXXXXX

I am using Paypal Business Account and I did API update and collected the Details above with XXXXXXX - inputs pasted in the fields

and submitted it. After that, I used front end page for Payment Submission I am getting Error  

Oh oh! Page not found.

Please help me to resolve ...