Nothing works

Thanks for testing the new editing experience. I am sorry this sounds like you got a bug on first activation. I would love to try and get that fixed for you, would you be able to create a bug here: https://github.com/WordPress/gutenberg/issues/new. If not could you perhaps let me know a bit more information as to how that invalid response occurred? For example, what browser were you doing and where you using a particular block when it happened?

How do you go back to traditional editing?

Plan B – https://www.ads-software.com/plugins/classic-editor/