This step requires access – either a cleanout plug or cutting into drywall. If you’re not comfortable with plumbing, skip to Step 6.

Before touching anything:

If snaking the standpipe doesn’t work, the P-trap (the curved pipe under the floor or behind the wall) is likely blocked.

This is the most common point of failure for front-loading machines. Washing machine drain clogged? Here's how to fix it - Homie