OK, I think I caused this by copying a bit too much from the old system. The automatically generated folder name eb4c25cfca709f93859e44c91e35ea28 did not exist but there was a folder with a different name. I copied the existing folder to one with the new name and the renewal worked flawlessly.
This still doesn't explain to me why the dry run reports complete success. That is VERY frustrating for people like me who rarely need to interact with these tools.