encoding rtf subtitles

[Valentina_23]

Hi everyone,
I have am mgp file and an rtf with subtitles. Both files have the same name. I try to encode the subtitles but i can't. I follow the path>subtitles>add subtitles, but when I play the film the subs aren't visible. Years ago it was enough to play the video with a subs file with the same name in the same folder to see the film subtitled. Now it isn't possible anymore.
Can anybody help me, please?
Thank you so much.
Best,
Valentina