Contact Agent Form Error 500

Hi,
I have an active Joomla Developer Membership;
What is the fix for the "Contact Agent Form Error 500" ?
Thanks

Hi Charlotte,
Thanks for contacting us and choosing our product!
Sorry for the late reply. I had a vacation day.
Please send me an account site via private message. I will to check help you
Thanks!

Hi NT,
I just sent you all details via PM
Thanks for your note

Hi Charlotte,
Sorry I've installed your site failure. There is a little problem, I want to talk to you. Please send me your mail.
Thanks!