Title: Activation error on 3.8.1
Last modified: August 21, 2016

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# Activation error on 3.8.1

 *  Resolved [lumega](https://wordpress.org/support/users/lumega/)
 * (@lumega)
 * [12 years, 3 months ago](https://wordpress.org/support/topic/activation-error-on-381/)
 * Hi Myatu, i can’t activate the plugin i recive this worning:
 * Warning: call_user_func() [function.call-user-func]: First argument is expected
   to be a valid callback in XXX/wp-includes/functions.php on line 2117
 * Warning: require_once(__DIR__/vendor/Symfony/Component/ClassLoader/UniversalClassLoader.
   php) [function.require-once]: failed to open stream: No such file or directory
   in XXX/wp-content/plugins/Archivio/vendor/pf4wp/lib/bootstrap.php on line 106
 * Fatal error: require_once() [function.require]: Failed opening required ‘__DIR__/
   vendor/Symfony/Component/ClassLoader/UniversalClassLoader.php’ (include_path=’.:/
   opt/php54/lib/php’) in XXX/wp-content/plugins/Archivio/vendor/pf4wp/lib/bootstrap.
   php on line 106
 * I’m hosted on hostgator php 5.4
    You can help me please? Thanks
 * [http://wordpress.org/plugins/background-manager/](http://wordpress.org/plugins/background-manager/)

Viewing 1 replies (of 1 total)

 *  Thread Starter [lumega](https://wordpress.org/support/users/lumega/)
 * (@lumega)
 * [12 years, 3 months ago](https://wordpress.org/support/topic/activation-error-on-381/#post-4538521)
 * I resolv ….

Viewing 1 replies (of 1 total)

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 * 1 reply
 * 1 participant
 * Last reply from: [lumega](https://wordpress.org/support/users/lumega/)
 * Last activity: [12 years, 3 months ago](https://wordpress.org/support/topic/activation-error-on-381/#post-4538521)
 * Status: resolved