Can't add any .srt file to the movie

Hi,
I've WD My Cloud connected to my LAN. I've a SONY Android TV installed KODI. I can access all files over KODI but I can't add any subtitle to the movie.

I've a structure like below.
Movie.mkv
Movie.srt

But Kodi doesn't recognize any .srt file. How can I fix that.

Thanks.