OK, so the fuel and oil were right - please confirm that there was enough fuel, so it couldn't have run out.
Next step is to verify that there is spark. The usual way to do that is to remove the spark plug from the engine, attach the plug lead to the spark plug, put the speed control in the start position, hold or clamp the metal outside body of the spark plug to a metal part of the engine, preferably the cylinder head, and pull the starter. There should be a series of tiny blue sparks across the gap in the spark plug between two tiny metal bits at the end of the threaded part: the dirty part of the spark plug that was inside the engine and is now covered with blackish stuff. The sparks should appear when the engine is spinning, and not otherwise.
