When the filter looks clean but airflow is still poor, the problem may be inside the blower, ducts, or coil

https://www.slideserve.com/katterobac/how-same-day-ac-repair-restores-cool-comfort-fast

When the filter looks clean but airflow is still poor, the problem may be inside the blower, ducts, or coil. Do not keep forcing the system; request a full inspection.