Does not work with posts

Hello!
I installed the plugin and it works with pages.
When i start a new post or open an existing one the window where you can edit the contents appears for one moment and then dissapears! And then there is no way to get it back-
I see everything about the post – the window for the title, the settings for the post. But there is no window for editing the content of the post!

P.S. and i still see the “gutenberg” button and can’t get rid of it.

The page I need help with: [log in to see the link]