I had just finished deploying a model between environments and tried to validate when I got this message:

MDSERR400038|Unpublished business rules exist. Apply the business rules before running Business Rules or Validation again.

The error message on this one is pretty straightforward. I had a list of business rules to publish and tried to set them all as active with a SQL update instead of using Master Data Manager. It didn’t work. I updated the business rules manually and was then able to process the model.