Answer: Since the plant is blooming well, I would suspect one of two things is causing the berries to disappear. One would be summer pruning, since the berries follow the flowers and would thus be inadvertently removed. The other would be that animals are eating the berries -- they are palatable to many songbirds, small mammals and deer. They may develop and be devoured while still green or just as they ripen to red and so you never have a chance to really notice them. I hope this helps you troubleshoot.
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