Answer: Unfortunately, based on your description I am not certain what happened. Bananas need ample sunlight (full sun all day long) and moist but well drained soil. If placed in too dark a location and consistently overwatered, or the container is left sitting in a saucer of water, there can be rotting problems with the roots and/or stem. Root problems are often signalled by foliage that dries out or browns, due to circulatory issues, as well.
This type of problem can be difficult to diagnose long distance. If something like this happens again, it is a good idea to consult with the retailer where you purchased the plant and/or your local county extension right away. Often a plant can be saved if the problem is diagnosed early enough.
If the plant has not regrown since June, then I think it is sadly probably dead. Monrovia is a wholesale only nursery, so any warranty would be based on the policies of the retailer where you purchased it. I am really sorry about your banana plant.
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