FileBot

command i used:
filebot -get-subtitles "x:\xxx\BlackRock.mkv" --q "black rock" -non-strict

output:
Get [English] subtitles for 1 files
Looking up subtitles by filehash via OpenSubtitles
Searching for [black rock] at [OpenSubtitles]
No matching subtitles found: blackrock.mkv
Done ?(?????)?


however, if i go directly onto opensubtitles page and search for "black rock" , there are multiple english subtitle exists for the movie. is this a bug? or am i doing something wrong?

You can try with the GUI and do a search for "Black Rock" and see if you get results. Might be an issue with OpenSubtitles website being different from the XML-RPC service for 3rd party programs.