Returning workspace outputs is supported with only single return argument

Hello

I am trying to connect simulink model with matlab coding forotimization purpose. Earlier for few models it worked. But now I am getting the error "Returning workspace outputs is supported with only single return argument". Please help me in this regard.

[Fangjun Jiang]

Are you using sim() command? You need to provide more details (lines of code) and MATLAB versions.

[Anagha Bhattacharya]

I am using Matlab simulink 2018b version. I have connected workspace and trying to control it through optimization algorithms. The error i am getting is "returning workspace output is supported with only single return arguments"