The rebloomers are interesting types of irises. Some kinds produce new flowers soon after the old ones die and others produce new flowers later in the season. Even though plants are bred as rebloomers, they may not produce a second set of flowers in a year, however. The ability depends on environmental conditions as well as genetics. Though I don't know the specific problem that is stopping your plant from reblooming, I can describe some reasons why irises fail to rebloom.
Many rebloomers won’t produce a second crop of flowers in the more northerly and cooler zones of the United States. It’s important to buy a variety that can rebloom in these conditions if this is where you live. If the nights are consistently warm the plants may not rebloom either, depending on the variety. Some types need a cooling period in order to produce more than one set of flowers.
The plants need extra care in terms of water and fertilizer to enable them to produce two or more sets of flowers in a year. They likely won’t rebloom in their first year of life but may when they are two or more years old. The rhizomes will probably need to be divided and replanted more often than those of irises that aren’t bred to rebloom.