n-channel igbt connected in series

Hello,I need to make a full bridge inverter with simscape parts.I have connected successfully pwm pulses with pwm generator from simpowersystems and the problem is that the n-channel igbts connected in series do not respond as they should... note that I've already made a full bridge inverter with simpower ideal igbts and works perfect... the reason i decided to migrate from simpowersystem to simscape is because i want a more specified igbt with more parameters to change.. any ideas..???