Error with AWS SFTP Transfer Server

I’m trying to create a vanilla AWS SFTP server. Terraform creates the resources, but the service cannot place a file on the remote location. I must be missing something simple. When I try to put a file I get this.

sftp> put number.txt
Uploading number.txt to /number.txt
remote open("/number.txt"): No such file or directory (5.8 KB)