Error message email received about potential denial of payment processing

-- url of the page with the problem -- : www.veggievore.com
-- HikaShop version -- : 3.0.1
-- Joomla version -- : 3.6.5
-- PHP version -- : 7.0.16
-- Error-message(debug-mod must be tuned on) -- : Hello,
A payment authorization notification was refused because the response from via the payment server was invalid. The hash received was 8ff60edf1c23b4931ab0eaa04901a6c5f590743843b9f6fc72875693b08d3a749be13aeb2111f0eb8b52f945109bb2d346211ff1512e3d36445eaca4165f7482 while the calculated hash was . This typically indicates an attempt to artificially place an order.

I received an automated email from my system that there was a potential problem with a transaction. The purchaser use Braintree Processing.

I am not sure if this error came from HikaShop, the Braintree plubin or Braintree itself. I have never seen this error before. Do you have any idea what generated this email:

Hello,
A payment authorization notification was refused because the response from via the payment server was invalid. The hash received was 8ff60edf1c23b4931ab0eaa04901a6c5f590743843b9f6fc72875693b08d3a749be13aeb2111f0eb8b52f945109bb2d346211ff1512e3d36445eaca4165f7482 while the calculated hash was . This typically indicates an attempt to artificially place an order.

Thanks for letting me know.