Well there have been several posts (mine included) about using FR24 to give you a sporting chance of finding out whether there actually is an aircraft in a position to operate your flight.
If there isn't, then that tells you all you need to know.
If there is an aircraft sitting at your gate, then a delay is more than likely either a crewing issue or a technical problem. If you can see the activity (if any) around the aircraft, then that's a good clue that they are trying to fix something.
Sorry if you haven't found those posts helpful.