Files won’t display on tablet and TV – external HD on a router

Hi, I use a USB HD connected to the router as a primitive NAS. I have a specific account enabled to access to shared folders and had no problems whatsoever with my windows pc’s on LAN or with ES explorer’s network function on my Android tablet and “smart” tv. I installed KODI everywhere yesterday. Despite accessing the folders with ease, the files are not displayed. I’ve checked the permissions, firewalls, etc., and I have no restrictions or barriers. Do you know whyu?