My plants have beautiful purple foliage and are 3 feet tall but no blooms. Seems I remember them blooming by this time last year.
Hibiscus plants need very warm temperatures in order to bloom, so if it hasn't been warm in your zone until lately, that could be the simple reason you're not seeing blooms yet. They also need lots of light, high humidity and fertilizer. Check to make sure you don't actually have buds that are falling off before they have a chance to bloom. These articles may help you: