Too little light
This is the single most common reason a Peace Lily won't flower, and it's a direct consequence of how forgiving the plant is about everything else. Peace Lily can survive — genuinely survive, for years — in fairly dim corners, which is exactly why it's marketed as a low-light plant. But surviving on dim light and blooming on dim light are different thresholds. Flowering takes noticeably more energy than maintaining leaves, and a plant getting only enough light to get by simply doesn't have the surplus to spend on it.
The pattern that points here: leaves that look a little pale rather than deep green, more space than usual between new leaves, and a general lean toward whatever light source the plant can find.
Fix: move it to bright, indirect light — a spot a few feet from an east or north-facing window, or set back from a sheer-curtained south or west one. Give it 2 to 3 months after the move before expecting flowers; the plant needs time to build up reserves before it commits energy to a bloom.
Wrong time of year
This is the fact most care guides skip, and it explains a specific, common complaint: a Peace Lily that flowered perfectly well in spring and then simply stopped, with no obvious change in care. Peace Lily is photoperiodic, meaning it reads day length, not just light intensity, to decide when to start forming flower buds. Buds for a spring bloom are typically initiated the previous winter, during the shorter, darker days of December and January — a plant sitting through the long days of June, July, and August is past that seasonal window and won't start new buds no matter how well it's cared for in the meantime.
Fix: nothing to fix — this one resolves itself with the calendar. If everything else here checks out and it's currently mid-summer, the most likely answer is simply that it's between blooming windows.
Store-bought bloom wearing off
A common and specific scenario: the plant arrived home already covered in flowers, put on a beautiful show for weeks, and then went completely quiet — sometimes for a year or more. Growers routinely treat Peace Lilies with a plant hormone (gibberellic acid) before sale specifically to force a full, uniform bloom for retail displays. It works, but it's a one-time push rather than the plant's normal rhythm, and once that effect wears off, the plant needs to build its own reserves back up before it flowers under its own steam again.
Fix: patience, plus getting the fundamentals right — bright indirect light and regular feeding through spring and summer. Don't expect the same density of blooms as that first retail display; a healthy, mature plant blooming naturally typically produces flowers in smaller flushes once or twice a year rather than all at once.
Needs feeding
A Peace Lily can hold onto healthy-looking leaves for a long time on very little in the way of nutrients, but flowering draws on reserves that ordinary leaf maintenance doesn't touch. A plant in good light that's simply never been fed is a common, easy-to-miss cause.
Fix: feed with a balanced liquid houseplant fertilizer during spring and summer, following label dilution — roughly monthly is enough for most homes. Skip feeding in winter, when the plant naturally slows down.
Still too young
A Peace Lily grown from a small starter plant needs time to mature before it flowers at all, regardless of how good its care is — often a year or two. If the plant is otherwise thriving, putting out new leaves steadily, and simply hasn't been around long, this may just be a matter of waiting it out.
Fix: keep conditions good — bright indirect light, regular water and feeding — and give it time. There's no way to safely rush this one.
Root-bound (a little is fine — a lot isn't)
This is a case where the usual houseplant advice doesn't quite apply. Peace Lily is one of the few common houseplants that often blooms better when its roots have some room to feel snug in the pot, rather than swimming in freshly repotted soil — some mild root-bound stress seems to nudge the plant toward flowering. That said, there's a real upper limit: a plant with roots so tightly packed they're circling in solid rings or forcing their way out of the drainage holes is stressed rather than encouraged, and that crosses from helpful into a genuine problem.
Fix: if it's only mildly snug in its pot, leave it — don't repot just because you're troubleshooting a lack of blooms. If roots are visibly overcrowded or escaping the pot, that's a separate problem worth fixing with a repot one size up, after which it may take a season to resume flowering as it adjusts.