Master-slave JK flip flop (74HC73) doesn't toggle
You need to connect the /R input to Vdd (called Vcc on 74HC chips). Floating, you have a good chance of holding the FF in reset.
All inputs to a 74HCxx chip should be tied to a valid logic level, including the unused flip-flop. Unused outputs can be left open.
You should also have decoupling capacitors across the power supply, preferably one near each chip package. 100nF ceramic is fine.