It's still ambiguous. Are you saying you subscribed to the threads in question but it didn't work? If so, you should post this problem in Site Feedback and Suggestions. It almost sounds like you expected to be automatically subscribed. You have to actively subscribe to any particular thread.

You can set a default in your UserCP to always subscribe to threads that are created by you. Have a look at that. Otherwise as mailpup says, you need to manually subscribe to certain threads by using the "Thread Tools" at the top right corner of each thread.