Why does washed laundry smell damp?
Take the laundry out when the cycle ends. A few hours in a wet closed drum can bring the smell back even to clean clothes.
Check the amount of detergent against the label. Too much rinses out poorly, and too little may not deal with the soil.
Leave the laundry room to move. A tightly packed drum washes and rinses the fabric less thoroughly.
Hang items loosely and let air move around them. Slow drying keeps the damp smell going.
If the earlier checks did not help, clean the door seal, the drawer and the filter, then run a service cycle the way the manufacturer describes.