Thank you for the reply, Citation issue has been resolved.
Upon checking the Error Log, I received following error:
PHP Fatal error: Uncaught Error: Call to a member function getProperties() on null in /lib/pkp/plugins/oaiMetadataFormats/dc/PKPOAIMetadataFormat_DC.php:44
Stack trace:
#0 /plugins/oaiMetadataFormats/dc/OAIMetadataFormat_DC.php(34): PKP\plugins\oaiMetadataFormats\dc\PKPOAIMetadataFormat_DC->toXml(Object(APP\submission\Submission), NULL)
#1 /lib/pkp/classes/oai/OAI.php(825): APP\plugins\oaiMetadataFormats\dc\OAIMetadataFormat_DC->toXml(Object(PKP\oai\OAIRecord))
#2 /lib/pkp/classes/oai/OAI.php(566): PKP\oai\OAI->formatMetadata(‘oai_dc’, Object(PKP\oai\OAIRecord))
#3 /lib/pkp/classes/oai/OAI.php(95): PKP\oai\OAI->ListRecords()
#4 /pages/oai/OAIHandler.php(47): PKP\oai\OAI->execute()
#5 [internal function]: APP\pages\oai\OAIHandler->index(Array, Object(APP\core\Request))
#6 /lib/pkp/classes/core/PKPRouter.php(334): call_user_func(Array, Array, Object(APP\core\Request))
#7 /lib/pkp/classes/core/PKPPageRouter.php(277): PKP\core\PKPRouter->_authorizeInitializeAndCallRequest(Array, Object(APP\core\Request), Array, false)
#8 /lib/pkp/classes/core/Dispatcher.php(165): PKP\core\PKPPageRouter->route(Object(APP\core\Request))
#9 /lib/pkp/classes/core/PKPApplication.php(388): PKP\core\Dispatcher->dispatch(Object(APP\core\Request))
#10 /index.php(21): PKP\core\PKPApplication->execute()
#11 {main}
thrown in /lib/pkp/plugins/oaiMetadataFormats/dc/PKPOAIMetadataFormat_DC.php on line 44