Thanks Dan. My json looks pretty similair to the one you posted.
Looks similar to me, so this is probably not the problem. I am using ngrok since I am developing under docker on my laptop. The email gets sent fine. The problem is that the link address in the FA template email starts "http://localhost:9011". I understand that is where my copy of FA is located on my laptop, but the email has been sent to a different machine! localhost:9011 won't work on a different machine!
So my link (in the passwordless email) needs to start with http://XX659b34a122.ngrok.io/. I know this link works fine because when i type it into the browser address bar on the remote machine, it opens my survey fine.
So how to get FA to send a link starting with my ngrok-http: instead of http://localhost:9011???
Also: is there anyway to set the FROM: address in the email dynamically using templates? The employees getting the passwordless emails will probably be wary of clicking an email from firstname.lastname@example.org rather than from taxmanagers_name@SomeCompany.com.