Astable Multivibrator Doesn't Vibrate
I would add a resistor between base of q3 (q1e) and negative rail (q2e). Then another larger resistor to limit base current in q3.

This change will unbalance the astable but you could balance it back by adding on q1e the same resistor as the q2e.

The load needs interfaced between positive rail and q3c.

As for resistor values, I would start with base current on q3, giving me base resistor, which leads to q1e resistor min 10 times smaller than base resistor on q3.also q3e is tie to negative rail. Hope this helps.
Hope this helps.