Update SKU using entity ID in import

I am trying to update sku using entity id and it’s working but issue is when i try to order that product from the front-end it shows “There are no source items with the in stock status”.
What to do?

This is my code.

<?
namespace CustomKapilModelImport;

use Exception;
use MagentoFrameworkAppResourceConnection;
use MagentoFrameworkDBAdapterAdapterInterface;
use MagentoFrameworkJsonHelperData as JsonHelper;
use MagentoImportExportHelperData as ImportHelper;
use MagentoImportExportModelImport;
use MagentoImportExportModelImportEntityAbstractEntity;
use MagentoImportExportModelImportErrorProcessingProcessingErrorAggregatorInterface;
use MagentoImportExportModelResourceModelHelper;
use MagentoImportExportModelResourceModelImportData;

/**
 * Class Courses
 */
class Courses extends AbstractEntity
{
    const ENTITY_CODE = 'learning';
    const TABLE = 'catalog_product_entity';
    const ENTITY_ID_COLUMN = 'entity_id';

    /**
     * If we should check column names
     */
    protected $needColumnCheck = true;

    /**
     * Need to log in import history
     */
    protected $logInHistory = true;

    /**
     * Permanent entity columns.
     */
    protected $_permanentAttributes = [
        'entity_id'
    ];

    /**
     * Valid column names
     */
    protected $validColumnNames = [
        'entity_id',
        'sku'
    ];

    /**
     * @var AdapterInterface
     */
    protected $connection;

    /**
     * @var ResourceConnection
     */
    private $resource;

    /**
     * Courses constructor.
     *
     * @param JsonHelper $jsonHelper
     * @param ImportHelper $importExportData
     * @param Data $importData
     * @param ResourceConnection $resource
     * @param Helper $resourceHelper
     * @param ProcessingErrorAggregatorInterface $errorAggregator
     */
    public function __construct(
        JsonHelper $jsonHelper,
        ImportHelper $importExportData,
        Data $importData,
        ResourceConnection $resource,
        Helper $resourceHelper,
        ProcessingErrorAggregatorInterface $errorAggregator
    ) {
        $this->jsonHelper = $jsonHelper;
        $this->_importExportData = $importExportData;
        $this->_resourceHelper = $resourceHelper;
        $this->_dataSourceModel = $importData;
        $this->resource = $resource;
        $this->connection = $resource->getConnection(ResourceConnection::DEFAULT_CONNECTION);
        $this->errorAggregator = $errorAggregator;
    }

    /**
     * Entity type code getter.
     *
     * @return string
     */
    public function getEntityTypeCode()
    {
        return static::ENTITY_CODE;
    }

    /**
     * Get available columns
     *
     * @return array
     */
    public function getValidColumnNames(): array
    {
        return $this->validColumnNames;
    }

    /**
     * Row validation
     *
     * @param array $rowData
     * @param int $rowNum
     *
     * @return bool
     */
    public function validateRow(array $rowData, $rowNum): bool
    {
        if (isset($this->_validatedRows[$rowNum])) {
            return !$this->getErrorAggregator()->isRowInvalid($rowNum);
        }

        $this->_validatedRows[$rowNum] = true;

        return !$this->getErrorAggregator()->isRowInvalid($rowNum);
    }

    /**
     * Import data
     *
     * @return bool
     *
     * @throws Exception
     */
    protected function _importData(): bool
    {
        switch ($this->getBehavior()) {
            case Import::BEHAVIOR_DELETE:
                $this->deleteEntity();
                break;
            case Import::BEHAVIOR_REPLACE:
                $this->saveAndReplaceEntity();
                break;
            case Import::BEHAVIOR_APPEND:
                $this->saveAndReplaceEntity();
                break;
        }

        return true;
    }

    /**
     * Delete entities
     *
     * @return bool
     */
    private function deleteEntity(): bool
    {
        $rows = [];
        while ($bunch = $this->_dataSourceModel->getNextBunch()) {
            foreach ($bunch as $rowNum => $rowData) {
                $this->validateRow($rowData, $rowNum);

                if (!$this->getErrorAggregator()->isRowInvalid($rowNum)) {
                    $rowId = $rowData[static::ENTITY_ID_COLUMN];
                    $rows[] = $rowId;
                }

                if ($this->getErrorAggregator()->hasToBeTerminated()) {
                    $this->getErrorAggregator()->addRowToSkip($rowNum);
                }
            }
        }

        if ($rows) {
            return $this->deleteEntityFinish(array_unique($rows));
        }

        return false;
    }

    /**
     * Save and replace entities
     *
     * @return void
     */
    private function saveAndReplaceEntity()
    {
        $behavior = $this->getBehavior();
        $rows = [];
        while ($bunch = $this->_dataSourceModel->getNextBunch()) {
            $entityList = [];

            foreach ($bunch as $rowNum => $row) {
                if (!$this->validateRow($row, $rowNum)) {
                    continue;
                }

                if ($this->getErrorAggregator()->hasToBeTerminated()) {
                    $this->getErrorAggregator()->addRowToSkip($rowNum);

                    continue;
                }

                $rowId = $row[static::ENTITY_ID_COLUMN];
                $rows[] = $rowId;
                $columnValues = [];

                foreach ($this->getAvailableColumns() as $columnKey) {
                    $columnValues[$columnKey] = $row[$columnKey];
                }

                $entityList[$rowId][] = $columnValues;
                $this->countItemsCreated += (int) !isset($row[static::ENTITY_ID_COLUMN]);
                $this->countItemsUpdated += (int) isset($row[static::ENTITY_ID_COLUMN]);
            }

            if (Import::BEHAVIOR_REPLACE === $behavior) {
                if ($rows && $this->deleteEntityFinish(array_unique($rows))) {
                    $this->saveEntityFinish($entityList);
                }
            } elseif (Import::BEHAVIOR_APPEND === $behavior) {
                $this->saveEntityFinish($entityList);
            }
        }
    }

    /**
     * Save entities
     *
     * @param array $entityData
     *
     * @return bool
     */
    private function saveEntityFinish(array $entityData): bool
    {
        if ($entityData) {
            $tableName = $this->connection->getTableName(static::TABLE);
            $rows = [];

            foreach ($entityData as $entityRows) {
                foreach ($entityRows as $row) {
                    $rows[] = $row;
                }
            }

            if ($rows) {
                $this->connection->insertOnDuplicate($tableName, $rows, $this->getAvailableColumns());

                return true;
            }

            return false;
        }
    }

    /**
     * Delete entities
     *
     * @param array $entityIds
     *
     * @return bool
     */
    private function deleteEntityFinish(array $entityIds): bool
    {
        if ($entityIds) {
            try {
                $this->countItemsDeleted += $this->connection->delete(
                    $this->connection->getTableName(static::TABLE),
                    $this->connection->quoteInto(static::ENTITY_ID_COLUMN . ' IN (?)', $entityIds)
                );

                return true;
            } catch (Exception $e) {
                return false;
            }
        }

        return false;
    }

    /**
     * Get available columns
     *
     * @return array
     */
    private function getAvailableColumns(): array
    {
        return $this->validColumnNames;
    }
}