Reviews Slider can be added to a page as a Gutenberg block. If you receive an error message saying that the block cannot be previewed after adding the Reviews Slider block, check the Developer Console in your browser for any JavaScript errors.
If you have Polylang plugin installed and receive the following error in the Developer Console, then the problem is caused by a bug in the Polylang plugin. Please make sure that you have updated the Polylang plugin to the latest version.
TypeError: Cannot set property 'lang' of null
