"Stella" that does not rebloom may not be true 'Stella de Oro'. I bought plants three times from garden centres, big box stores, etc., and general plant nurseries that were sold as Stella that never rebloomed. They were not Stella. I finally bought a true Stella from a specialist daylily seller. It reblooms. My wife did not know I had Stella and bought one labelled as Stella at a general plant nursery three years ago. It does not rebloom; it is not a true Stella (determined from characteristics by comparison with true Stella).
Rebloom is dependent on how the plant is grown as well as where it is grown. I am in Zone 4 with a growing season on the shorter side. I can grow a daylily cultivar so it never reblooms for me or I can treat it so that it grows at its best rate in my zone and it will rebloom for me. The simplest example is 'Mosel'. It never rebloomed for ten years. Then I started mulching it, weeding it, watering and fertilizing it. After one year of being treated to better growing conditions the fans had increased in size and it rebloomed. It reblooms every year if I treat it well.
From the opposite side I can take the Stella that reblooms and get it to no longer rebloom simply by not fertilizing it, not watering it and not dividing it.
I am not suggesting that all daylily cultivars can rebloom in all locations. If a cultivar requires a long growing season to rebloom for example, when grown well in Florida it blooms in April and then reblooms in October I will not be able to get it to rebloom in my location. I probably cannot get cultivars that bloom late to rebloom for me since they would never have enough time in my location.
