@Marpu 

Hi,

The amount of formats that TVs can play via DLNA is often rather limited.

What is the make and model of your TV?

  @woozle  I tried connecting the TV to the computer as a DLNA server and it finds and plays all the videos there without a problem. So the error is in the router, it can't share it relevantly. I'm going to return it to the dealer and buying a another mark. This one is sh*t.

  @Marpu 

Just a word of caution before you decide on your next router model.

The DLNA media servers on router's like the Archer C6U are only capable of serving a media file "as is".
If the player device doesn't support the format of that particular media file to be played via DLNA, then it either won't play or not show up at all. 

However, DLNA media server software for computers, like for example "Universal Media Server" or the DLNA Media Server already built into Windows 10 and 11, will "transcode" the media file to a supported format if the player doesn't support the original format. Usually this happens without the user noticing. 
Basically the media server software decodes and then re-encodes the media file in the background before sending it to the player.

I really doubt that any router in the price range of the Archer C6U is capable of transcoding media files.
 

  @Marpu 

Probably you had already returned. I'm posting here anyway to register my opinion.

The problem is with the router as it mounts the file .TPDLNA that is a map of the disk for the DLNA Client. I use ROKU box.

First it takes a long long long time to mount it, then if you are lucky it maps ALL the folders and files from the disk, which most of the time it doesn't map all forders and files.

I'm still spending hour and hours trying to find a way to make it work and trying to find a trick that fix it, like deleting the .TPDLNA folder and let it create again. Sometimes it works and for my surprise after a few hours something is not there anymore. Once it showed some folders duplicated and just one of them was real.

Sometimes renaming a folder or a file force it to show up. Also it does not like files which name starts with numbers.

As I have my router for a while now, return it is not a option. A easy solution is to connect the drive to the ROKU or TV USB, but will not be shared disk anymore.

It is a big BUG that looks like all TP-LINK routers have as I read on this forum. It's a router operating system bug and they don't care.