Try to fix Following way..
Open below file
vendor/magento/module-import-export/Controller/Adminhtml/Export/Export.php
and replace below function
public function execute()
{
if ($this->getRequest()->getPost(ExportModel::FILTER_ELEMENT_GROUP)) {
try {
$params = $this->getRequest()->getParams();
$model = $this->_objectManager->create(\Magento\ImportExport\Model\Export::class);
$model->setData($this->getRequest()->getParams());
$this->sessionManager->writeClose();
return $this->fileFactory->create(
$model->getFileName(),
$model->export(),
\Magento\Framework\App\Filesystem\DirectoryList::VAR_DIR,
$model->getContentType()
);
/** @var ExportInfoFactory $dataObject */
$dataObject = $this->exportInfoFactory->create(
$params['file_format'],
$params['entity'],
$params['export_filter']
);
$this->messagePublisher->publish('import_export.export', $dataObject);
$this->messageManager->addSuccessMessage(
__('Message is added to queue, wait to get your file soon')
);
} catch (\Exception $e) {
$this->_objectManager->get(\Psr\Log\LoggerInterface::class)->critical($e);
$this->messageManager->addError(__('Please correct the data sent value.'));
}
} else {
$this->messageManager->addError(__('Please correct the data sent value.'));
}
/** @var \Magento\Backend\Model\View\Result\Redirect $resultRedirect */
$resultRedirect = $this->resultFactory->create(ResultFactory::TYPE_REDIRECT);
$resultRedirect->setPath('adminhtml/*/index');
return $resultRedirect;
}
Please don't forget to clear cache after change in files