Answer: How perplexing! Obviously you are doing things right because one is blooming so well and both have grown well. The most likely possibility I can think of is that the nonbloomer was mislabeled and is not the same rose at all. Another possibility is that for some reason it has not established quite as well, perhaps due to different soil conditions. (Soil often varies from one bed to the next depending on the garden's history and how the builder filled around the foundation.) Unfortunately, the only way to know for sure is to wait for it to bloom.
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