There are many reasons why a vacuum loses suction, including clogged, dirty, or unreplaceable filters. There might also be foam or mesh filters in your vacuum cleaner. All of these filters need to be regularly cleaned and replaced to ensure proper airflow and suction. You should start by checking your vacuum filters first, as this is often the cause of suction loss. It is also a wise idea to check the vacuum's hoses and tubes for blockages that may prevent air from flowing freely. You may need to replace the vacuum's motor or belt if there are no blockages.