Webstorm: Why is "upload to default server" gray/deactivated?

I'm using the ftp client in Webstorm. An ftp server is set up properly and I can browse it in the "Remote Host" tool window. Also the ftp server is set as default: enter image description here

However, I cannot upload or download enter image description here

Solution

While posting this question I just noticed that my mappings were not set up properly: Both web-host and deployment path should have been specified.

(Maybe someone else is as stupid as me and will find this helpful.)