simulation warning message in ADS! PLS HELP!

I am designing a multi band antenna and i use ADS to simulate it, i have some warning message when it simulating the S-parameters:
inaccuate (high frequency ) calibration;
electrically large via using lumped model;
higher order modes at the ports;
grouped strip-slot ports;
mesh density is too coarse;



can anyone tell me why did this happen?
thanks!

i think you need calibration again... Maybe you have to calibrate and increase distance frequency

i am using a partial ground plane for my antenna ( using layer cond2)
should i place a port on layer cond2 to ground it?
or only one port on layer cond for input is enough?

I met the same warning. Can someone offer more explanations on how to handle this?