Your browser does not seem to support JavaScript. As a result, your viewing experience will be diminished, and you have been placed in read-only mode.
Please download a browser that supports JavaScript, or enable it if it's disabled (i.e. NoScript).
Edit:
It's because one of my text fields had an emoji in it.
Cannot.
I've tried the same thing as you and for me it's working in RUN mode. Have you managed to make it work?
Bad IP. Change your proxy.