There is usually a drainage compartment on the front of the washing machine. Try that, it collects stuff that can eventually stop water getting out. The first thing to try as you don't have easy access to the drain is doing a cycle that uses the hottest setting which is normally 90. That may do the job. To get at the drain one normally has to just pull the washing machine out by hand. Have a bucket or something to catch water as it could get messy.