My Hibiscus had one bloom when I got it but has never blossomed since, though it is healthy, shiny and well cared for. It's now 6 years later. How do I make it bloom?
It sounds like a healthy green plant that may have been fed too much nitrogen.
Excess nitrogen in the soil or over fertilizing will inhibit flowering.
You can do a soil test if your Hibiscus is in the ground.
Adding some phosphorous can help boost flower production.
Bone Meal is a good way to do this.
Here are some links with information.