Without lecturing you, Abby, and being completely objective and without any prejudice as I've never heard you sing or perform,

...sounds like for whatever the reason, you failed to make any kind of a connection with the audience.

Could have been attributable to any or all of the following:

(a) They didn't like the song.
(b) They didn't like your voice.
(c) They're not into acapella.
(d) They weren't listening.
(e) They were totally apathetic.
(f) The audience doesn't share your taste in music.

Perhaps, tape the tune, and have a few people who's opinions you respect and trust, and who can be (brutally if need be) objective, to listen to it, and get their feedback.

If you enjoy singing for the love of doing it, don't let this experience discourage you.

If on the otherhand, you need some sort of validation or recognition from an audience, then you must somehow find tunes to sing that WILL make the connection with them and yield the intended response.

My 0.02 anyway.