This is the most effective tool. Insert a hand-cranked plumbing snake into the standpipe. Feed it down until you feel resistance, then rotate the handle to "hook" the clog and pull it out.
If you have a front-loading machine, there is usually a small door at the bottom front. Place a towel down and open the door. Unscrew the filter (be ready for water to rush out). how to unclog washer drain pipe
Check the drain pipe for any visible blockages, such as lint or debris. If you find any, try to remove them by hand or with a pair of needle-nose pliers. This is the most effective tool