I had the same issue, and found a bug. The error / success messages don’t show unless you go to “Preview” and then “Back to Editor”.
I created a form using inputs, and connected this to the Team dataset. When I edit the submit button, I am not able to see where the error message is in the editor. When I click “add error message” or “add success message” nothing is visible. See Image 1 below.
I tried to add them, but couldn’t see anything. When I publish and go to the live site, there are multiple error messages, so clearly they are being added, just you can’t see them or edit them from the editor. I hit undo enough times to make them go away, and revert to the default.
I then tried the “Preview” and then went “back to editor” and could now see the error / success messages.
Seems to be a bug.
