Miss wilmots ghost
We have had the plant for three years now, it dies back in winter and grows back well through summer , when we first planted it it had a flower but hasn't flowered since.
It is likely that the plant lacks the proper nutrients or pH. You can put a fertilizer in that is high in P (phosphorus) and K (potassium) and help facilitate flowering.
You can also spread dolomitic lime around to control pH, as sometimes When that is off, it can cause a lockout.
Here is an article with more information: https://www.gardeningknowhow.com/ornamental/flowers/sea-holly/sea-holly-flowers.htm