Marina, has spotted an oddity. View the front page of your site and turn editing on. Using the "main menu" block, add a page. The page is created somewhere like /mod/page/view.php?id=81 and has a page type of "mod-page-view".
To be a subpage of the front page it should have a page type like "site-index-something" I believe. I'm not sure how these pages come to exist.
Currently if you add any blocks to the front page and set their "page contexts" to "Display on the front page and any pages added to the front page" then create pages via the main menu the blocks will not appear on those pages because their page type says they are related to mod-page and not site-index. Maybe this is correct. I don't know yet.