Despite being called a cactus, this is a epiphyte that grows in a rainforest, so perhaps you are letting it dry too much. It likes to be a little moist but definitely not soggy or dry.
Had the same happen to mine didn't water so it was all shriveled 🥲 finally decided to water it one day and it's been happier ever since noticed a couple new leaves last week plus there's roots everywhere🤗🌱
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