With Protea it is not unusual for them to take a year or two before they begin to flower. The reason being the flowers are so large the plant requires a strong “woody” branch to support the weight of the flower. When a protea is flowering it is at a very vulnerable stage and very sensitive to water stress.  Water at least every second/ third day until it is a well-established plant for at least the first two summers.     The best time of year to plant is autumn. Plant may have been pruned at the wrong time or to frequently.  Prune after flowering.