"Excuse me, where is the Subway?"
Translation:Извините, где метро?
It's most likely because "находится" hasn't been taught quite yet (at least I haven't run into it). It's good to know a lot of words, so definitely don't stop there. But, just stick to words that have been in lessons just while you're learning here, and you'll be fine. :)
(Also, make sure that you're being choosy with your words. The English translation isn't "Where is the subway located", just "Where is the subway?". The program, like any other of its kind, is very picky with what it will accept.)