Emacs -Q

With org-mode, hs-minor-mode: hs-show-all has no effect, but"Showing all 
blocks ... done" is messaged.

BTW M-x show-all RET works as expected.
See also attached png.

In GNU Emacs 25.1.91.1 (i686-pc-linux-gnu, GTK+ Version 3.14.5)
  of 2017-01-02
Windowing system distributor 'The X.Org Foundation', version 11.0.11604000
System Description:    Debian GNU/Linux 8.7 (jessie)

Configured using:
  'configure --with-modules'

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND GPM DBUS GSETTINGS NOTIFY ACL GNUTLS
LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB TOOLKIT_SCROLL_BARS GTK3 X11
MODULES

Important settings:
   value of $LANG: de_DE.utf8
   value of $XMODIFIERS: @im=ibus
   locale-coding-system: utf-8-unix

Major mode: Org

Minor modes in effect:
   tooltip-mode: t
   global-eldoc-mode: t
   electric-indent-mode: t
   mouse-wheel-mode: t
   tool-bar-mode: t
   menu-bar-mode: t
   file-name-shadow-mode: t
   global-font-lock-mode: t
   font-lock-mode: t
   blink-cursor-mode: t
   auto-composition-mode: t
   auto-encryption-mode: t
   auto-compression-mode: t
   line-number-mode: t
   transient-mark-mode: t
   hs-minor-mode: t

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Hs minor mode enabled in current buffer
You can run the command ‘hs-minor-mode’ with M-x h-mi RET
Hs minor mode enabled in current buffer
Showing all blocks ... done
You can run the command ‘hs-show-all’ with C-c @ C-M-s
Showing all blocks ... done
Quit [2 times]

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rfc822 mml mml-sec
password-cache epg epg-config mm-decode mm-bodies mm-encode mail-parse
rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045
ietf-drums mm-util help-fns help-mode mail-prsvr mail-utils hideshow
org-element org-rmail org-mhe org-irc org-info org-gnus gnus-util
org-docview doc-view subr-x jka-compr image-mode dired cl-loaddefs pcase
cl-lib org-bibtex bibtex org-bbdb org-w3m org org-macro org-footnote
org-pcomplete pcomplete org-list org-faces org-entities noutline outline
easy-mmode org-version ob-emacs-lisp ob ob-tangle ob-ref ob-lob ob-table
ob-exp org-src ob-keys ob-comint comint ansi-color ring ob-core ob-eval
org-compat org-macs org-loaddefs format-spec find-func cal-menu easymenu
calendar cal-loaddefs time-date mule-util tooltip eldoc electric
uniquify ediff-hook vc-hooks lisp-float-type mwheel x-win
term/common-win x-dnd tool-bar dnd fontset image regexp-opt fringe
tabulated-list newcomment elisp-mode lisp-mode prog-mode register page
menu-bar rfn-eshadow timer select scroll-bar mouse jit-lock font-lock
syntax facemenu font-core frame cl-generic cham georgian utf-8-lang
misc-lang vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms
cp51932 hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese charscript case-table epa-hook jka-cmpr-hook help
simple abbrev minibuffer cl-preloaded nadvice loaddefs button faces
cus-face macroexp files text-properties overlay sha1 md5 base64 format
env code-pages mule custom widget hashtable-print-readable backquote
dbusbind inotify dynamic-setting system-font-setting font-render-setting
move-toolbar gtk x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 8 213298 12008)
  (symbols 24 44887 0)
  (miscs 20 90 204)
  (strings 16 72650 6667)
  (string-bytes 1 1431280)
  (vectors 8 18599)
  (vector-slots 4 529123 7854)
  (floats 8 212 87)
  (intervals 28 279 0)
  (buffers 520 18)
  (heap 1024 41653 932))