This kind of den will not bloom without enough light. Your leaves are a little green, you may want to set it in a brighter window. I finally got a batch of my dens to bloom this summer by changing their location. I moved them to a very sunny corner porch that still has good afternoon shade. Once they got lighter green and were sporting a few burn dots I began to see spikes. And I agree with the above, it is normal to lose a few lower leaves from time to time.