Honestly, no
I just tested on your site. After I enter my email address, the form goes away (as expected), but never re-appears. It should come back one way or another with a "Success" or "Fail" type message.. yours is just staying blank. That could be because the server isn't responding, a fatal error we didn't catch somewhere, or something else... but not sure off-hand from what I'm seeing.
Can you Private Message me the following:
* FTP credentials to get into your files. We'll need to edit and setup breakpoints to test
* The 'list ID' from Sendy (the 20'ish character string) that should be submitted too?
You can PM me by clicking the mail icon under my name to the left.
Everything else, we should be able to determine from there.
Thanks,
Alex