Translation:I am sick, I can't attend your party.
@Andrew - in your own English database, how have you marked the word "like"? e.g. if I say "I like you", what does your database understand? And if I say "I am like you", what does it understand? Finally, "I like people like you" and "I like people who like you". If you made correction on your database then I'm sure you'd have translated most of these sentences wrongly. Above was just one me. Now multiply it by twenty million (others' variations / suggestions / outraged complaints). That's the problem Duo Lingo has to deal with.
Chinese doesn't really have past tense the same way English does. It means something about the past or a change. The best way to think about it in cases like this one is that it could literally translate to "I got sick" or "I became sick". I wasn't sick before but now I am. I've seen other languages that would translate it in a similar way to how Chinese does.