Client email missing error, when client email isn't missing

I’ve got a handful of existing zaps (that have been working fine) until I went in to make a small amendment to one today.

The zaps are triggered by a Jotform submission, and the action is to create a new project in Dubsado. Today I created a new workflow in Dubsado and so wanted to create change that detail in one of my zaps - so that it would apply that workflow when the new project was created. 

But when I test the zap, I get this error message;
Failed to create a project in Dubsado
Required field "Client Email" (client__email) is missing.

The client email is not missing. I went to the jotform on my website to submit manually with a valid email address, and it still wont create a new project. 

Next I went to my other working zaps to see if there was something I could spot that I’d missed when amending the other. And when I tested those (without changing anything within) they too are now coming back with the error.

What have I done? Can anyone help?