I had a serious mistake with the script I bought from you

Hi.
I had a serious mistake with the script I bought from you.
I can’t make a payment through Mollie Payments on GeniusCart. When I click the Continue button I get 500 Internal server error! How can I fix it?
There is a Test API key from Mollie Payments in the admin panel.

Hi, please contact the author of the item to get support: