my registration process is not working

i couldn't figure out why people were registering for my site then not completing the payment section to gain access but now that i've tried testing it over and over again, it's not working. anyone can register but when they go to "SIGNUP" for a membership they get the message "Sorry, your signup request has failed. Try again. " but when you try again you get the same message.

can someone help me trouble shoot this ASAP???