My rose of Sharon gets buds but fall off before blooming.
Rose of Sharon
Certified GKH Gardening Expert
Usually buds drop off of Rose of Sharon bushes when the plant has been distressed in some way. Not enough water or (if you live in a harsh winter climate) damaging hail or winds can cause it. This article may help you: https://www.gardeningknowhow.com/ornamental/shrubs/rose-of-sharon/rose-of-sharon-bush.htm