Ming arelia leaf drop
Arapahoe County Colorado
Ming Aralia is considered a tropical plant, which are a challenge to grow in Colorado homes. The normal environment of tropical plants is very sunny, very warm and very humid, so you have to do your best to create this same environment if you want the plant to flourish.
Being tropical means it will suffer damage at generally 50°F and below. So if it is getting cold air from the opening and closing of nearby doors or the cold air or drafts from nearby windows, it should be moved.
Tropical plants such as this require high light and temperatures not less than 60°F; and the brighter the light and warmer the temperature, the better. It should be placed in the sunniest and warmest place in the home.
Tropical plants perform better in humid environments. Dry air in Colorado homes can be improved with a humidifier placed in the room the plant is in. The pot can also be set on top of (not in) a tray of pebbles that contains water. See photo below.
Ming Aralia also requires consistently moist soil at all times—but not wet—so this can be a delicate balance. Insert your index finger into the soil; if it is dry, it needs water but make sure the water drains well. Moisture will need checked several times a week. Without consistent moisture, the plant cannot support growth so will shed leaves to conserve water.
You didn't mention the age of the plant. This plant prefers confined roots so make sure it is not is too large of a pot.
Finally, some leaf drop from this plant is normal, even in its native tropical environment.