Magento 2 – How to Remove SID (Session ID) from URL

it seems your session not set properly for your ssl url,

you check for the cookies that

1. Ensure you have mod_headers.so enabled in Apache instance

2. Add following entry in httpd.conf

   Header edit Set-Cookie ^(.*)$ $1;HttpOnly;Secure

3. Restart Apache Web Server

Note: Header edit is not compatible with lower than Apache 2.2.4 version. You can use following to set HttpOnly and Secure flag in lower than 2.2.4 version. Thanks to Ytse for sharing this information.

Header set Set-Cookie HttpOnly;Secure

Open your website with HTTP Watch, Live HTTP Header or HTTP Header Online tool.

Check HTTP response header, you should see as highlighted

If you look at the class Magento\CatalogUrlRewrite\Model\CategoryUrlPathGenerator which is responsible for the category URL rewrite generation, you will see that it uses a constant value to determine if the parent path should be added:

protected function isNeedToGenerateUrlPathForParent($category)
{
    return $category->isObjectNew() || $category->getLevel() >= self::MINIMAL_CATEGORY_LEVEL_FOR_PROCESSING;
}

The value is

const MINIMAL_CATEGORY_LEVEL_FOR_PROCESSING = 3;

which means the path is generated for every category that is not a top category (level 1 is the root category) and you cannot configure this value or turn off parent path generation.

And since it is a protected method we cannot modify the return value with a plugin. Instead you will have to write a plugin for the public method getUrlPath() that uses isNeedToGenerateUrlPathForParent().

I would use an around plugin which does not call the original method, essentially replacing the method:

class RemoveParentCategoryPathPlugin
{
    public function aroundGetUrlPath($subject, $proceed, $category)
    {
        if (in_array($category->getParentId(), [Category::ROOT_CATEGORY_ID, Category::TREE_ROOT_ID])) {
            return '';
        }
        $path = $category->getUrlPath();
        if ($path !== null && !$category->dataHasChangedFor('url_key') && !$category->dataHasChangedFor('parent_id')) {
            return $path;
        }
        $path = $category->getUrlKey();
        if ($path === false) {
            return $category->getUrlPath();
        }
        return $path;
    }
}

(this is the original method, but without the parent path generation)

Plugin documentation: http://devdocs.magento.com/guides/v2.1/extension-dev-guide/plugins.html

Update existing categories

This will apply for new categories. Unfortunately the category URLs are not generated by an indexer anymore, so reindexing does not change them and the only way to regenerate them is to save each category. It could be done with a one-off script that loads a collection of all categories and calls save() on it:

$allCategories = $categoryCollectionFactory->create()->load();
foreach ($allCategories as $category) {
    $category->setDataChanges(true);
    $category->save();
}

Note that this is not optimized for performance at all and will load all categories at once. So if you have thousands of categories you might want to process them in batches.