Such a bummer when bulbs don't bloom! In late summer it is too late to convince agapanthus to send up those beautiful blue flower spikes. To encourage flowers next summer you may need to dig and divide the bulbs in the fall or early spring so they are not crowded or if the bulbs were just planted give them another year in the ground to mature and grow large enough to support flowering stems. Full sun, well drained soil and using a slow release plant food with all the micro plus macro nutrients  (like Osmocote) will help your agapanthus fulfill its full potential. Keep growing, Marianne Binetti