Thanks to @Armin for finding a bug in this thread: Samba stopped and can't restart:
When installing “File server” from Software Center it still appears in “Available Software”. The packages are installed, I can use the “Shared Folders” in web UI.
When I try to install it on command line with
yum groupinstall "File server" I get an error:
Warning: Group nethserver-file-server does not have any packages to install.
No packages in any requested group available to install or update