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LT3753, Active clamp forward converter design

Iam designing a low power (10W) Active clamp forward converter, PWM modulator used to drive main MOSFET and Auxiliary MOSFET is LT3753.Specification are input voltage range: 26V - 42V, Output 5V, operating at 500kHz.In closed loop control i am getting the steady 5V output. The simulated circuit is as shown in figure below.

Tried to do in open loop by removing the opto-coupler connection and connected a constant voltage of 550mV as shown in figure below.

The below waveform shown are at ISENSEP and at COMP pin.

I am implementing same open loop in hardware but in hardware i am not getting the gate pulse. when i checked the voltage at 'COMP' pin its showing me '900mV' instead of  '1.95 V' as in simulation. How should i proceed further in hardware.

Thanking you in advance.