Problems with dependent dropdowns

I have a problem with dependent dropdowns in EventBooking.
When I get to the payment page, I want to have two fields depending on each other. But when I pick in the first field, the next field doesn't change.

Maybe something wrong with your settings. Please submit a support ticket :

1. Sending me admin and FTP account of your site.

2. Let me know what field is a depend on which field

I will check to see what's wrong with the settings and get it corrected for you.

Regards,

Tuan