There are some young leaves so there is growth. Since you brought your plant inside, it may go through a light source change. Some leaves may start dropping off while new leaves grow adapted to the new conditions. You might see less color in the leaves but that will go back once it is outside again.
Some of your stems look very mature so they won't be as lush and full. You want to encourage branching off of that. Did your plant go to flower?
If it were my plant, I would cut the tallest stem back to the new stems growing lower down, put that cutting in water and let it root. I would even pinch back the second longest stem at the tip but you could wait and see how it adjusts first. It will help your plant bush out and put out fresh stems. At some point you will notice a lot of growth, especially as you get into spring.
Window light isn't ideal but coleus can tolerate it. Just make sure it isn't getting direct sunlight through the window. That could burn the leaves. Here that would be a South facing window. Is it the same by you? I have a shear between the window and my plant.
How long has it been in that pot?
