Many different factors may affect your entitlement to compensation. If you flew from an airport outside Europe to a European destination with a non-EU airline, your flight unfortunately does not fall under the Regulation. All flights that are operated entirely outside of the EU also do not entitle you to compensation, as the Regulation strictly applies to the EU.
It’s also possible your flight falls outside of the restrictions mentioned above but you’re still not entitled to compensation. This may be the case if you left with a delay of 3 hours or more but arrived at your destination under 3 hours late. This often occurs when pilots accelerate to catch up, or as a result of the cross-Atlantic jet stream. Because only the delay in arrival counts toward the official delay, you would also not be entitled to compensation in this case.