This was a silly mistake on my part, but when I searched for the error, I didn’t come up with any results, so I thought I would post it in case it helps someone else.

I had created a sync rule that saved without any errors. When I tried to add it as an activity to a workflow, I got the error:

“workflow could not be validated as at least one activity had a configuration error”

It turns out I had added an attribute flow mapping in the sync rule to the DN. Took that out and I could create the workflow.