Notice the input field doesn’t show the cursor when you click on it and it doesn’t show the email address as you are typing it. But the typing does work and you can submit the form.
Our Contact Form module text color is set to inherit whatever color the closest DOM to it is set to. For your case, the column color text color is set to white so it’ using that. You can use the CSS snippet below to change it though.
That fixed it. I would make some sort of notation about that on the subscribe form. It’s a simple fix, but I didn’t even think to look at the css text color. It just looked like a form bug to me.