BLock plugin does not work

Same for me.

You need to add classes to [/BLOCK] also.

It works for me on WP-4.3.1 and Customizr theme; albeit with a bit of a skewed layout (a lot of extra space in left column between “Fields marked with an * are required” and first field.) You both remembered to add the following to your CSS, correct?

.njf-column {
    display: inline-block;
    width: 49.5%;
}

@iczek , @airsid this plugin provides blocks functionality, columns can be result in case you are using css, like an example css provided in FAQ.