Re****t prep DTS step?

When running the dw population DTS task, it gets all the way through except
for the last step: "Re****t Preparation". The error just says "Re****t
preparation failed." but nothing more descriptive. There were no logs
generated for additional info. How can I find out why this step failed?
Where do I look?

Also, how can I find out what this step is actually doing. I don't see a
property page??

Thanks!