Help with payment 2checkout Check key is incorrect

Hi this is my first install of dolphin software onto my membership site, I want to use 2checkout for my membership fees but I keep on getting the same message, "Check key is incorrect" what does this mean? I have used the information here to set up all the settings but when I am returned to my site after cc payment using 2checkout it says Check key is incorrect, can someone help me as I cant find information on it.

I'm beginning to worry that many issues that are posted on the support forum are not being addressed since many have no replies to customer questions. Makes me worried that support will not be their when needed most.

I have the same issue with 2Checkout that you are having and so far 2CheckOut hasn't been very helpful either.

DM