It's hard to say why flowers were lacking on that portion of the shrub, but if it receives more shade from the canopy of the nearby Crapemyrtle, that might be one reason. Most of last year's growing season was in drought for much of the state, so if the plants weren't occasionally irrigated as needed, maybe it didn't have enough moisture in late summer, when this year's flower buds were developing, to form or maintain those buds through the winter. Was any part of those upper branches pruned between last July (or so) and this spring? If so, that would have removed flower buds, even if new foliage regrew.

We don't see lace bugs or scale either, but if they were present, depriving the plant of some vigor last year might have impacted how well it flowered, though we'd doubt the consequences would have been that localized to only those upper branches.

For now, you don't need to do anything about it, though if that growth winds-up looking weaker as the growing season progresses, it can be pruned back to stimulate replacement growth.

Miri