I have upgrade magento 18.104.22.168 from Magento 22.214.171.124 now a guest customer can visit the product page, but when the logged-in customer visit the product page it is showing the error as below:
"SQLSTATE: Integrity constraint violation: 1062 Duplicate entry '1561-232' for key 'UNQ_REPORT_VIEWED_PRODUCT_INDEX_CUSTOMER_ID_PRODUCT_ID', query was: INSERT INTO
added_at) VALUES (?, ?, ?, ?, '2019-06-26 07:06:34') ON DUPLICATE KEY UPDATE
When I comment the below line in file
"Code\Core\Mage\Catalog\Helper\Product\View.php" the line number 135 code is
Mage::dispatchEvent('catalog_controller_product_view', array('product' => $product)); then it is allowed to load the product page for logged in customer and logged out both.
Please let me know if anything you found for the issue.