[android tv] mx player can't find subtitles

Hi there

I installed mx player on my android tv box (freebox mini 4k) and when I watch video I click on search online subtitles, entering movie title and it shows nothing...
I configured languages preferences in the app settings (french + english).

Am I missing something ?

I am watching movies from macbook using plex media server if it's helpfull...

Thx by advance