issue relating opto coupler HPCL 3120

[arr_baobao]

im currently using a optocoupler HPCL 3120 to drive the switches in my two switches forward converter project. first i had tested the optocoupler output to gives the correct waveform into the switches.
After that i try to test the whole circuit with a smaller input voltage which is 50Vac. when i connect the input voltage to my circuit, i lost the waveform i got previously that is the waveform from the HPCL 3120 to the switches of my 2 switches forward converter. Then i try to remove the input voltage and check again with the waveform produces by the HPCL 3120, i can't get any waveform, just flat line.
so what happened to my circuit? i had try to changed the HPCL 3120 chip and the switches, but there's stil no responce from the output of the HPCL 3120. anyone here can helps me pls?
thanks
i will attach my circuit diagram and the hpcl 3120 connection here.

 

[mtwieg]

You'll have to give a more specific schematic showing how the optocouplers are connected to the FETs, and how they are powered. The high side drive needs a floating or bootstrapping supply voltage to work properly.

Also what's with L3 being coupled to the forward transformer? I've never seen that before...

 

[arr_baobao]

the Vo of the opto is connected to the the gate of the FET and the ground is connected to the source of FET. 15Vdc are provided to the Vcc to run the opto coupler. evrything i fine with the optocoupler and the switch before i start connecting the main circuit with the input voltage source 50Vac. after i connect, i lost evrythings like i mentioned before.

HELPS pls

 

[mtwieg]

Is the 15V supply for the high side optocoupler isolated, or ground referenced?

A complete schematic would make things much easier. A verbal description isn't going to help much.

 

[arr_baobao]

the high side optocoupler is isolated bro