Certified GKH Gardening Expert
I suspect that it could be a few things.
Lighting is important. They don't tolerate direct sun. They are well adapted to low light condition, and will prefer moderate to low, indirect light.
Watering is important. Because these are epiphytes, they grow on other trees, and not in the ground. Since this is in soil, then the soil likely remains too wet. This will cause brown tips. Soil is not the best medium for the plant, but it will tolerate it as long as it has a chance to dry out a little from time to time.
The last consideration will be nutrient contents. If this is anything other than a cactus soil, seedling mix, or any other mix that is light without much nutrients, then it can suffer from too much nutrients.
Here is an article that will help you to provide proper care to the plant: