If you don't see a subscription on your Subscriptions page and you have already added the bank or credit card account that it is charged to, you can add it from your list of transactions.
You can do this from your Dashboard with your spending.
Find the subscription from your Spending category. Click on the gray icon to the right of the charge and then select This is a subscription from the drop-down menu.
Refresh your Subscriptions page and you should see your newly-added subscription on the list.