0 - One of the required plugins is missing or not enabled

I'm trying to install grav for the first time. I downloaded a skeleton and I added admin plugin manuelly (with admin, email form and login in user/plugin).
But i have this message (see title) instead of admin page.
What can I do ?

Logs : [2016-04-21 13:19:11] grav.CRITICAL: One of the required plugins is missing or not enabled - Trace: #0 /home/gilleskl/public_html/grav.monsite.pro/user/plugins/admin/admin.p hp(263): Grav\Plugin\AdminPlugin->initializeAdmin() #1 [internal function]: Grav\Plugin\AdminPlugin->onPluginsInitialized(Object(RocketTheme\Toolb ox\Event\Event), 'onPluginsInitia...', Object(RocketTheme\Toolbox\Event\EventDispatcher)) #2 /home/gilleskl/public_html/grav.monsite.pro/vendor/symfony/event-dispa tcher/EventDispatcher.php(181): call_user_func(Array, Object(RocketTheme\Toolbox\Event\Event), 'onPluginsInitia...', Object(RocketTheme\Toolbox\Event\EventDispatcher)) #3 /home/gilleskl/public_html/grav.monsite.pro/vendor/symfony/event-dispa tcher/EventDispatcher.php(46): Symfony\Component\EventDispatcher\EventDispatcher->doDispatch(Array, 'onPluginsInitia...', Object(RocketTheme\Toolbox\Event\Event)) #4 /home/gilleskl/public_html/grav.monsite.pro/vendor/rockettheme/toolbox /Event/src/EventDispatcher.php(23): Symfony\Component\EventDispatcher\EventDispatcher->dispatch('onPlugins Initia... ', Object(RocketTheme\Toolbox\Event\Event)) #5 /home/gilleskl/public_html/grav.monsite.pro/system/src/Grav/Common/Gra v.php(449): RocketTheme\Toolbox\Event\EventDispatcher->dispatch('onPluginsInitia.. .', NULL) #6 /home/gilleskl/public_html/grav.monsite.pro/system/src/Grav/Common/Gra v.php(259): Grav\Common\Grav->fireEvent('onPluginsInitia...') #7 /home/gilleskl/public_html/grav.monsite.pro/index.php(38): Grav\Common\Grav->process() #8 {main} [] []
[2016-04-21 13:19:12] grav.CRITICAL: One of the required plugins is missing or not enabled - Trace: #0 /home/gilleskl/public_html/grav.monsite.

I think there is an error in this files https://learn.getgrav.org/admin-panel/faq#manual-installation-of-admin

because I downloaded the core and admin panel package, and it's working

Mmmm looks like one of those plugins is not installed or enabled.

Are they installed as /user/plugins/email, /user/plugins/login, /user/plugins/form ?

Also, looks like those links you used point to the develop branch, which is the development version.

I now fixed the links.

You'd better re-download them from the Plugins page where the latest stable version is available.

OK thank's for your help.