[THz antenna in CST MWS ] Maximum simulation time reached， solver stopped ?

I am trying to simulate an sntenna at 0.3 THz. I m using a wave-guide port to excite it. Its a simple patch antenna structure with SiO2 as substrates. I came across the following error.
"Maximum simulation time reached, solver stopped."
I know this error can be resolved by increasing the "Number of pulses" from 20 to a higher number. I have increased it till 400, but still the error appears. Any other solution to this error.
Awaiting replies,
Regards

Maybe you have some simulation problems, for example, check the energy diagram if the system energy decays with time. And post a pic of your setup.