Gardenias need high humidity so when indoors they thrive near a sink or in a humid bathroom. They also like bright but indirect sunlight and should not be allowed to dry out. The because problem is spider mites which causes the leaves to yellow and drop and can show up as webbing on the foliage. Spray the foliage with water often to keep the plant free of mites and also to increase the humidity. Fertilize with a slow release plant food like Osmocote but don't use more than the package suggests. Keep the plant away from cold drafts and excess heat. This is not an easy houseplant to make happy so if you do get yours to flower again send us a photo and we'll all celebrate your success. Keep growing, Marianne Binetti