Omeka1.5 problem with Ubuntu 14.04

we are using Omeka 1.5, it works fine with Ubuntu 12.04.

After upgrading ubuntu from 12.04 to 14.04, it seems work fine but the /oai-pmh-repository/request?verb=ListRecords&metadataPrefix=oai_dc shows errors:

Zend_Controller_Dispatcher_Exception
Invalid controller specified (oai-pmh-repository)

#0 /var/www/heritage/application/libraries/Zend/Controller/Front.php(954): Zend_Controller_Dispatcher_Standard->dispatch(Object(Zend_Controller_Request_Http), Object(Zend_Controller_Response_Http))
#1 /var/www/ourheritage.ac.nz/application/libraries/Zend/Application/Bootstrap/Bootstrap.php(97): Zend_Controller_Front->dispatch()
#2 /var/www/heritage/application/libraries/Zend/Application.php(366): Zend_Application_Bootstrap_Bootstrap->run()
#3 /var/www/ourheritage.ac.nz/application/libraries/Omeka/Core.php(165): Zend_Application->run()
#4 /var/www/heritage/index.php(29): Omeka_Core->run()
#5 {main}

Any help will be appreciated.
Thanks

Is the OAI-PMH Repository plugin installed and activated?

Thanks, good point. Actually after upgrading, all plugins were deactivated. It is solved after activating the plugins.