It's hard to determine what is wrong with your tree without more information, but having grown one of these in the past, I noticed it did better after it was replanted. That's because the original site provided too much shade and weeping cypress prefers full sun. Whenever you have a plant that is dying, look for site conditions that are contributing to the decline: sun vs. shade, poor drainage, hot, drying winds--things like that can stress a plant and make it more susceptible to pests and diseases. Also, look for signs of pests and diseases--boring holes in the wood, whole branches and limbs turning brown at once, etc. When you see those indications, seek help from a professional arborist or bring a sealed sample to your local extension office.
Luke Miller, editor
Garden Ideas & Outdoor Living magazine