PayFast Plugin not working

Hi

I just bought a Payfast plugin & set it up in a website using (EShop - used to work with Offline, but now want to add PayFast).
We've also redesigned the website, so everything is still on localhost.

When trying to make a pyament via PayFast, we get the following:

NOTICE & the payment does not go through Payfast (See images)

This website needs to go alive today.

Hello Jacs,

I think the reason because you did not enter PDT Key parameter in the payment plugin. Please continue to following up the ticket system to get our supports.

Sincerely, Giang