dokku: Dokku 0.5.6 returns "Please run: sudo dokku plugin:install" on each plugin request

Description of problem: I’ve just installed dokku and run postgres plugin install command: sudo dokku plugin:install https://github.com/dokku/dokku-postgres.git dokku returns:

-----> Cloning plugin repo https://github.com/dokku/dokku-postgres.git to /var/lib/dokku/plugins/available/postgres
Cloning into 'postgres'...
remote: Counting objects: 561, done.
remote: Total 561 (delta 0), reused 0 (delta 0), pack-reused 561
Receiving objects: 100% (561/561), 112.69 KiB | 0 bytes/s, done.
Resolving deltas: 100% (345/345), done.
Checking connectivity... done.
-----> Plugin postgres enabled
-----> Migrating zero downtime env variables. The following variables have been deprecated
=====> DOKKU_SKIP_ALL_CHECKS DOKKU_SKIP_DEFAULT_CHECKS
=====> Please use dokku checks:[disable|enable] <app> to control zero downtime functionality
=====> Migration complete
=====>
Adding user dokku to group adm
start: Job is already running: nginx

But when I’ve tried to create postgres db with: dokku postgres:create db_name dokku returns me an error Postgres: Please run: sudo dokku plugin:install

When I’m trying to: sudo dokku plugin:install It returns:

sudo dokku plugin:install
-----> Migrating zero downtime env variables. The following variables have been deprecated
=====> DOKKU_SKIP_ALL_CHECKS DOKKU_SKIP_DEFAULT_CHECKS
=====> Please use dokku checks:[disable|enable] <app> to control zero downtime functionality
=====> Migration complete
=====>
Adding user dokku to group adm
start: Job is already running: nginx

But it doesn’t solves the problem.

Output of the following commands

• uname -a: Linux alext 3.13.0-86-generic #130-Ubuntu SMP Mon Apr 18 18:27:15 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
• free -m:

total       used       free     shared    buffers     cached
Mem:          2001       1592        409          0         53       1327
-/+ buffers/cache:        212       1789
Swap:            0          0          0

• docker version:

Client:
 Version:      1.11.1
 API version:  1.23
 Go version:   go1.5.4
 Git commit:   5604cbe
 Built:        Tue Apr 26 23:30:23 2016
 OS/Arch:      linux/amd64

Server:
 Version:      1.11.1
 API version:  1.23
 Go version:   go1.5.4
 Git commit:   5604cbe
 Built:        Tue Apr 26 23:30:23 2016
 OS/Arch:      linux/amd64
- `docker -D info`:
Containers: 0
 Running: 0
 Paused: 0
 Stopped: 0
Images: 3
Server Version: 1.11.1
Storage Driver: aufs
 Root Dir: /var/lib/docker/aufs
 Backing Filesystem: extfs
 Dirs: 6
 Dirperm1 Supported: false
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
 Volume: local
 Network: bridge null host
Kernel Version: 3.13.0-86-generic
Operating System: Ubuntu 14.04.4 LTS
OSType: linux
Architecture: x86_64
CPUs: 2
Total Memory: 1.955 GiB
Name: alext
ID: MMQ5:VZC2:5Q4I:QLMK:3L4H:BR23:JVI2:RDVY:LJT6:SEUV:S2GO:MPDU
Docker Root Dir: /var/lib/docker
Debug mode (client): true
Debug mode (server): false
Registry: https://index.docker.io/v1/
WARNING: No swap limit support

• sigil -v: 0.4.0
• docker run -ti gliderlabs/herokuish:latest herokuish version:

  emberjs.tgz                latest
  buildpack-nginx            v5
  heroku-buildpack-clojure   v75
  heroku-buildpack-erlang    fa17af9
  heroku-buildpack-go        v34
  heroku-buildpack-gradle    v17
  heroku-buildpack-grails    v20
  heroku-buildpack-java      v44
  heroku-buildpack-multi     v1.0.0
  heroku-buildpack-nodejs    v90
  heroku-buildpack-php       v101
  heroku-buildpack-play      v26
  heroku-buildpack-python    v80
  heroku-buildpack-ruby      v146
  heroku-buildpack-scala     v70

• dokku version: 0.5.6
• dokku plugin:

plugn: dev
  00_dokku-standard    0.5.6 enabled    dokku core standard plugin
  20_events            0.5.6 enabled    dokku core events logging plugin
  apps                 0.5.6 enabled    dokku core apps plugin
  build-env            0.5.6 enabled    dokku core build-env plugin
  certs                0.5.6 enabled    dokku core certificate management plugin
  checks               0.5.6 enabled    dokku core checks plugin
  common               0.5.6 enabled    dokku core common plugin
  config               0.5.6 enabled    dokku core config plugin
  docker-options       0.5.6 enabled    dokku core docker-options plugin
  domains              0.5.6 enabled    dokku core domains plugin
  enter                0.5.6 enabled    dokku core enter plugin
  git                  0.5.6 enabled    dokku core git plugin
  logs                 0.5.6 enabled    dokku core logs plugin
  named-containers     0.5.6 enabled    dokku core named containers plugin
  nginx-vhosts         0.5.6 enabled    dokku core nginx-vhosts plugin
  plugin               0.5.6 enabled    dokku core plugin plugin
  postgres             1.0.0 enabled    dokku postgres service plugin
  proxy                0.5.6 enabled    dokku core proxy plugin
  ps                   0.5.6 enabled    dokku core ps plugin
  redis                1.0.0 enabled    dokku redis service plugin
  shell                0.5.6 enabled    dokku core shell plugin
  storage              0.5.6 enabled    dokku core storage plugin
  tags                 0.5.6 enabled    dokku core tags plugin
  tar                  0.5.6 enabled    dokku core tar plugin