If water doesn’t clear, you need to physically break up the clog.
If the blockage is further down the pipe, try using a garden hose to flush out the debris. Insert the hose into the drain and turn on the water. The pressure from the hose may be enough to dislodge the blockage. how to unblock outdoor drains
You can buy a "drain jetter attachment" for a standard domestic pressure washer. This is a flexible hose with a specialized nozzle that shoots water backward to propel itself forward and blast debris away. If water doesn’t clear, you need to physically