以下提示什么意思，怎么解决？求大神指点?

No valid radiation output requests have been generated. This may be because no valid cavities exist in the model.

There is zero FORCE everywhere in the model based on the default criterion. please check the value of the average FORCE during the current iteration to verify that the FORCE is small enough to be treated as zero. if not, please use the solution controls to reset the criterion for zero FORCE.

There are 2 unconnected regions in the model.