Time to fertilize. When a healthy, shade loving annual like impatiens fails to flower  the most common cause is lack of fertilizer or perhaps too much high nitrogen plant food. Fertilizers made for lawns and houseplants have a heavy dose of nitrogen that encourages leaf growth at the expense of flower production. Just use a plant food made for blooming plants with the numbers 5-10-10 describing the ratio of nitrogen to potassium and phosphorus or simplify by looking at the label to see lots of flowers and words that say the formula is good for blooming plants. Osmocote is an example of a slow release plant food with a mix of nutrients that will encourage blooming. For faster results use a fast release plant food that mixes with water. Miracle Gro Bloom Boster is an example of this.   The middle number is the highest of the three numbers on the label so you know the NPK  formula has a lot of phosphorus to promote blooms. You should see your impatient full of buds and flowers in just a few weeks after a dose of flower fertilizer. Remember to read and follow the instructions on the label. Too much plant food can damage the plant. Keep growing, Marianne Binetti