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There are a number of solutions.

First make sure that all supply grilles are open and return registers are not blocked. Also, leave room doors open to alleviate some of the temperature discrepancy.

If you still have an issue there are a number of solutions. Essentially the room is cold because there is no heat getting to a room or because a room loses heat faster than the rest of the house. An HVAC contractor can determine if there is an airflow or duct issue. Ductwork may need to be replaced or balancing dampers in the ducts may need to be adjusted to provide proper air flow.