Error mounting a config file into the container

(I added the same problem few minutes ago.)

Make sure your docker is allowed to mount the directory C:\Users\[redacted]\Documents\Docker

Configuration

In the Windows client, you can configure the docker to allow read/write on specific drives. This should fix your permissions problem.

Already configured ?

In my case, it was already selected. I unchecked and checked the drive again. Apply the "change". It prompted me for my Windows password (which had change) and than the mount worked again.