Weigela blooms primarily on old growth (the stem growth produced the prior year), though it can also bloom on new growth (the stem growth produced the current year). This means that if the plant has been pruned (or browsed by deer, possibly) any time between autumn and spring, all of the first group of flower buds (which typically open in the May-June timeframe) will be lost and the plant cannot replace them. Some cultivars have been introduced in recent years which have improved reblooming capability, meaning they produce a lot more flowers on the new growth during summer.

Has your shrub been pruned in the past few years? Is it located in full sun, where it receives at least 6 hours of direct summer sun? If sited in too much shade, it may not flower well or might skip a year or more between blooms. If it's in a location near lawn which is fertilized regularly, it might be receiving more nitrogen than it needs, which tends to stimulate plants to produce foliage at the expense of flowers.

If none of these conditions applies, we aren't certain why it refuses to flower. A late frost might ruin flower buds, but that probably won't happen every year, and Weigela blooms late enough in the spring that frost injury is unlikely. (Plus, cold-singed foliage would be noticeable in that case.) Since Weigela is not native, you could replace it with a different species, especially if you prefer to use native shrubs. Lots of options exist, and narrowing them down will depend on site conditions along with what properties you want the plant to have (season of bloom, fragrance, native, deer-resistant, etc.).

Miri