It's hard to say for sure what someone's intentions are when they don't respond to you, but it's generally safe to assume that they're not interested if you've been trying to contact them and haven't gotten a response. There could be any number of reasons why they're not responding, and it's possible that they might be interested in you but just very busy or preoccupied with other things at the moment. If you're really interested in someone, though, it's best to just move on if you don't hear back from them after awhile.