Gardenia not blooming
These are mealybugs. They are tough to control and if you have valuable plants in addition to this one, which could be infested from this plant, then you may want to simply toss it.
Here's our webpage: https://extension.umd.edu/hgic/topics/mealybugs-houseplants
In addition, here's more Extension input about mealybugs:
Mealybugs are not easy to control. This is because the eggs are enmeshed in waxy fluff and thus relatively water proof. Likewise adults and nymphs can be covered in wax to varying extents and obscured in plant nooks and crannies where it is difficult to get thorough pesticide coverage.
For this reason systemic insecticides may offer the most reliable control because they make the plant toxic to feed on rather than relying on contacting the insect directly. If a contact insecticide is used be prepared to repeat the applications two or more times to kill nymphs that hatch from protected eggs and adults or nymphs that were protected by plant tissue. If an infestation is discovered early enough on a few cherished house plants, the mealybugs may be removed by a cotton swab dipped in alcohol or fingernail polish remover. Keep an eye on the plants for a few weeks to make sure no mealybugs are overlooked.
Putting houseplants outside over the summer where predatory insects can attack a pest insect on your plant sometimes provides the best pest control.
Gardenia's can be finicky bloomers. There are several reasons why they don't bloom. Bud drop is the most frequent complaint with gardenias. Some of the contributing factors are: lack of uniform or adequate soil moisture, low humidity, too warm or too cold conditions, rapid temperature fluctuations, and insufficient light. Insect pests also lower the plants’ vigor.
Be sure you are providing the basic cultural requirements also.