Please verify your settings under:
(rightclick >) Options > Preferences > Subtitles > [Subtitle properties]
Is the correct language (for you) selected at "Default subtitle language"?
(to disable subtitles: check the box at "Subtitles disabled")
((rightclick >) Options > Preferences > Subtitles >
) [Online subtitles]
Is "Enable online subtitles" selected and the box of the URL checked at "Online subtitle URLs"?
To select another subtitle as the one found automatically:
(rightclick >) Subtitles > Find subtitles manually ... etc.