Hi mills52_b, Welcome to EasyEDA. From the look of your screenshot, the only thing stopping your simulation from running is that you have chosen active parts (transistors and LEDs) that do not have spice models associated with them. To fix this please see (3) in: https://easyeda.com/andyfierman/Welcome_to_EasyEDA-31e1288f882e49e582699b8eb7fe9b1f If the astable doesn't start in the simulation even with the stepped voltage source you have (correctly) used to start up the circuit, you may also need to make the base resistors slightly different values. This is just for simulation purposes because in reality they will be different whereas in the sim they are *exactly* the same. When it is running, put a voltage probe on either base and note that as each transistor turns on, the base of the other is driven below ground. With a 9V supply, this will be by more than the reverse Vbe rating of the transistors. In a real circuit this would at least modify the operating frequency, at worst could blow the transistors. You do not see any effect in the sim because (for reasons that I have never understood!) bjt models do no model reverse Vbe breakdown. You can model it by putting a 3.3V zener in series with an ordinary diode from each base to ground so that for positive base voltages, the ordinary diode is reverse biased and for negative base voltages is is forward biased and the zener breaks down. This will be at about -4V because the 3,3V zener breakdown is in series with approximately 0.7V diode drop. Sounds complicated but try it. :)

Thank you. That got it working.