The error occurs because you have set the solver to fixed-step and specified the step size to be 0.001,which serves as the fundamental sample time of the model in the configuration parameters of the model ,but the sine wave block or other blocks in the model are set to a different sample time and not 0.001.In order to avoid the error either set the solver to variable-step or set the sample time in every block to 0.001 .
You can use ctrl+E or go to modelling---->model settings to change or reconfigure the settings in the configuration parameters window.
Refer to the below documentation link to get to know about the solvers
