i had the same problem with the yaml configuration files.
I found out that yaml is sensitive for formating (spaces and tabs), so you need a specific file structure!
The server will load the default settings, if the yaml structre is not correct.
Have a look at my config as a example, it works how I want it. (attached to this post)
You can upload it to your configuration and change the settings and remove the ".txt" ending in its file name.