How to use two or more cos functions in HFSS optimization setup?

Whenever I have two or more cost functions in optimization setup, my simulation ends after one variation. For example, if I want to set a cost function for S11, and another one for S21, optimization fails. Whatever design structure I have, I never got it to work. Could anybody help?

Sounds weird to me....

Try the following:
1. Make sure original simulation is working
2. Remove S11 specs, make sure optimizaiton is working only with S21 specs
3. Remove S21 specs, make sure optimizaiotn is working only with S11 specs

attach the error message if still not working.