Hi,
Since your subscription is active, the update is available to you, the issue is that Joomla is not detecting it. Joomla caches the update information, and that cache (or the HikaShop update site) often goes stale after a Joomla update, which is why it stopped showing. The HikaShop update check does not depend on the Joomla version, so the Joomla update only triggered the stale cache, it did not remove your access to the update.
Please try this first, in order:
1. In Joomla, go to System and use Clear Cache to clear it.
2. Go to System > Update > Update Sites and make sure the HikaShop update site is present and enabled.
3. Go to System > Update > Extensions and click "Find Updates" to force a fresh check.
4. Then look again, both in the Joomla extensions update list and in HikaShop's own update area in the HikaShop dashboard.
A manual update is not required, but it is the simplest fully reliable option if the cache refresh does not bring it back:
1. Log in to your account on hikashop.com and download the latest HikaShop Essential package from your My account>My subscriptions area.
2. In Joomla, go to System > Install > Extensions and install that package on top of your current installation.
This is safe. Installing on top does not touch your products, orders or settings, and you can go directly from 6.1.0 to the latest 6.5 in a single step, the installer runs all the required database migrations, so there is no need to install the intermediate versions one by one. It's the same as running the update from the Joomla extension update manager.