Why the ATC is not clearing me to take-off?

• Have a look on how the radio comunications are handled in EasyATC
• First, there is two clearances before starting a flight: a flight clearance and a take-off clearance. If you have a taxi chart, see the Taxi chart article for how requesting flight, taxi and take-off.
• First of all, make sure you have asked for a flight clearance. If you don't use any Taxi chart, you must ask this flight clearance to the ATC of the airport you are on (usually a Tower). If you use a Taxi chart for this airport, you must ask the flight clearance to the APRON waypoint.
• Check that you are using the right runway! Ask a take-off clearance and pay attention on the runway heading the ATC gives. Depending on the wind direction, the take-off runway can be different from the planned runway.
• If you are not using a taxi chart, you must be on the right side of the expected runway with the same heading (+/- about 10 degrees). Make sure the coordinates of the airport are as close as possible to the middle of the runway you want to take-off from: to know if you are ready for take-off, EasyATC processes the coordinates and heading of your plane with the coordinates of the airport and the heading of the expected take-off runway. 
• If you have a taxi clearance (see Taxi chart section), make sure you are within the trigger limit of the taxi waypoint (0.1 Nm by default, this value is displayed in the Debug text)
• You must trigger the airport
• You must talk to the appropriate ATC: any ATC that have the same CallSign that the aiport. For example if you take-off from Lima, you must contact a Lima ATC (Lima Tower or Lima Approach or Lima Departure). Note that Centers and FIS don't deliver take-off clearance.
• Finally, if you cannot have a take-off clearance, you can take-off and do a transit-in clearance after take-off (wait 10 seconds after leaving the ground to make sure the ATC is informed by X-Plane that you are now flying): everything should become normal for the rest of your flight. Don't hesitate to post your flight plan on the EasyATC forums so that I can found where the issue comes from.