What simulator are you using?
A few items that are obvious to me:
You should not let the center input of U1 and U4 leave floating. Tie it to ground as you did with the other inputs.
Use resistors to limit the curent through the LEDs. This may (or may not) be a nissue with the siulator, but it will be an issue in the real circuit.
Simulators assume ideal elements. Therefore the circuit is 100 % symmetrical. This is equivalent to a real world flipflip being in a metastate (being neither definitely high nor low). It may help, just for simulatin purposes, to introduce a deliberate asymmetry, Either the simulator allows to define an initial state (e.g. output of U3 = high, output of U2 = low) or add some pull-up and pull down resistors, e.g. 10 kΩ from the output of U3 to Vcc and another 10 kΩ from the output of U2 to ground. Depending on the simulator this may help.
Thar circuit is a simplified version that won't toggle, (at least not if at least the pulses is excactly timed and run time through each gate is about perfectly). The circuit you should look for is called "Master-Slave JK Flip Flop" - example on this site: https://www.electronics-tutorials.ws/sequential/seq_2.html