Do blog posts (not pages) have sidebars?
Possible Answers to Your Question:
There are 4 different sidebars in LayersWP by default – two of which are used for WooCommerce. It means that pages, categories, tags, archives, search, posts and possibly custom post types (+ taxonomies) will always use either a left or right sidebar.
If well understood your post single template does not display either sidebar which means they are disabled. Go to Customizer select
Blog > Posts & Pages
…and be sure to tick the checkbox next to required sidebar.