Q.Christmas Cactus has stopped blooming
My Christmas Cactus has stopped blooming and the leaves are not as dark green, thick and firm as they have been in former years. Can you tell me what may be causing this? We installed new energy efficient windows about 3 years ago with sun reflecting qualities to keep out the heat of summer. Could the windows be blocking the needed sun rays? These are plants that have been in my family since my grandmother had it (and that is a VERY long time – new growths have been started periodically from the plant to keep the original plant in the family). Leaves drop off now and are also quite limp. The only change made are the new windows. It used to bloom twice a year with MANY flowers and some stems with two buds! I’ll be so sad if I cannot keep this plant growing. Can you help?
You mentioned installing your windows three years ago. Has your christmas cactus been struggling for three years since they were installed or is this a new development this year? If this is a new development this year, then I don't think the windows are to blame.
Is it possible your christmas cactus has been over or under-watered?
When was your cactus last repotted? The general recommendation is to re-pot every 2-3 years so if it has been longer than that a re-potting might give it a much needed boost. When re-potting, examine the roots for signs of root rot and treat, if necessary (see https://www.gardeningknowhow.com/plant-problems/disease/treating-root-rot-gardening-tips-for-housplants.htm) . The article below will give you repotting guidelines as well as additional information on why christmas cactus go limp: