This plant likes non chalky, humus rich soil in shade (though a little sun won't hurt this particular one) and hates root disturbance, so no digging underneath its canopy. Can take 3-7 years to flower, so if the conditions you're growing it in are as described, hopefully next year you may get some flowers. Hope you're keeping it well watered during this drought.

If it's seedling rather than a named form it could take anything up to 20 years to flower. All the named forms of M. grandiflora are propagated by cuttings (and sometimes grafting) and will flower much younger, sometimes from just a few years of age.