Certified GKH Gardening Expert
This will be hard to diagnose without seeing the damage. I will give you the most common issues that can cause this. Without knowing its care, and seeing the exact damage, I won't be able to get you very far.
Too much or too little light will cause these symptoms. They need bright, but never direct light.
Too much too little water can cause this, as well. Too much water will suffocate the roots, leading to droopy plants, while too little water will starve them, leaving them droopy as well.
Too little humidity can cause wilting. This can be corrected by adding humidity.
Planting is soil, rather than orchid mix can cause wilting.
Too much or too little nutrients can also cause issues.
Unfortunately, they have some pretty strict requirements in order to keep them alive. Without knowing the conditions where the orchid resides, I can only give you examples of what can cause wilting.
This article will help you, further: https://www.gardeningknowhow.com/ornamental/flowers/orchids/indoor-orchid-care.htm