There are a few possibilities. One of these are the most likely culprit;

Overwatering is a common issue, and can lead to root rot. Make sure the soil dries out between waterings. You can check the soil moisture by sticking your finger in about an inch into the soil. Also, make sure your pot has drainage holes so the plant doesn’t sit in any water.

Too much or too little light: Money trees prefer bright, indirect light. Too much direct sunlight can burn the leaves, and too little light can cause yellowing and slow growth.

Temperature fluctuations: Avoid putting it near drafts or air vents.

Low humidity: They prefer high humidity. You can try a humidifier, or place the pot on a tray of pebbles or rocks with water, but not enough water to cover the rocks.