Not Acceptable! Error

Dear Author:

I use your plug free version very well for a long time.

Recently it could not process the payment correctly.

All the orders could not complete the payment and become to a cancelled order status finally.

I use the Paypal sandbox mode to test.

It shows an error message after pay as follow:

Not Acceptable!
An appropriate representation of the requested resource could not be found on this server. This error was generated by Mod_Security.

My website is VaporFan.com

I link a screenshot for you.

I use your plug very well before, and really like it.

Thank you very much for the help !!!

John Feng

The page I need help with: [log in to see the link]