Did you have a cold spell that may have killed the buds?
This is the most common reason for bud loss.
This tree is also susceptible to a few diseases.
Verticillium wilt sometimes attacks and kills forest pansy redbuds. The soilborne fungal pathogens invade the tree's roots and quickly spread throughout the entire vascular system.
Forest pansy redbud trees sometimes attract canker pathogens, particularly those that cause Cytospora canker. This fungal disease primarily occurs on trees suffering from environmental stress caused by winter injury, drought, sunscald or pruning wounds.