A few things could help. Mainly, it looks like it needs light. Find someplace where it gets direct sunlight for an hour a day, and slowly up the light, if possible. (A plant that gets direct sun, after going a long time without can burn. So do an hour a day for a week, then up it to several hours) If the soil stayed wet for several weeks, it may be holding too much water. Check and make sure there are drainage holes in the bottom of the planter. If even in the sun the soil doesn't dry out somewhat in a week, then I would get a different potting soil and re-pot the plant, removing whatever soil falls away easily, but not damaging the roots. It help sometimes to layer some rocks in the bottom to improve drainage. The last thing is feeding. I wouldn't do this until the plant has been in the sun regularly for a few weeks. and then every few weeks thereafter, the plant should get some food, as long as it is looking healthy (feeding is likely to burn an unhealthy plant). Find a food that is made for indoor flowering plants, and follow directions carefully. Many plants can tolerate shade, but they will go dormant and not produce flowers. Try the sun first, then try the others, and, barring disease, it should perk up and start blooming again.

Apparently I was wrong with the light. Peace lilies prefer less light, though putting it near a window where the sun won't shine directly on the foliage should help. Mine seems to do great right next to the window, getting a little direct light each day. But others recommend bright non-direct light. Good luck.