You should have made a starter with the washed yeast.
Stored yeast, washed or not, loses viability the longer it's stored. In the case of unwashed slurry, a good estimate is 25% loss per seven days stored. In other words, after a month it's pretty well shot. Washed yeast does better than that, but I don't have those numbers before me.
Before you do anything, take a gravity. You may have some activity. Hell, the improbable may have occurred and the ferment went by so fast you didn't even see it.
If the gravity is unchanged or little changed from the OG, I'd get some more yeast in there pronto. Frankly, I don't think you've got time to wait for a starter to get going. Hie thee to thy LHBS and get a packet of an appropriate dry yeast and get it going if necessary.