I tried this over and over again, deleting, creating, checking the database, but the nleft and nright values never changed.
Also disabled caching, cleared the cache. Created categories for one shop only, created categories for all shops, neither action changed the nright,nleft values, always = 0. I would really appreciate any help you could give, since I know not what to do else.
I'm using Prestashop 1.6.0.8, Multishop feature enabled, two live running shops. But unable to create new categories, alwas getting 404, and nleft/nright = 0.