This block has encountered an error and cannot be previewed

This plugin is exactly what we are looking for, but unfortunately it does not work.

After selecting the custom post type we would like to use from the ‘Post Type’ drop down the Gutenberg block instantly disappears and and error then appears in place of it that states ‘This block has encountered an error and cannot be previewed’.

Additionally, if we leave the post type as ‘Post’ and then try to save the page an error appears that states ‘Updating failed. The response is not a valid JSON response’.

We do have ‘show_in_rest’ set to ‘true’ for our custom post type.

Has this plugin been tested with the latest version of WordPress?