It is difficult to know for sure why you are not getting blooms.  The Mexican sunflower requires at least 6 hours of full sun for good blooming along with well-drained soil that is not too nutrient-rich.  If you have had a lot more rain than usual, or if overhead foliage is creating more shade than in the past, these could be factors in not have buds or flowers.  Too much fertilizer could also be a factor.  The link below from University of Wisconsin Extension has more information on the Mexican sunflower.
https://hort.extension.wisc.edu/articles/mexican-sunflower-tithonia-rotundifolia/