Based on user reports and debugging, the primary causes are:

The project opened like an old song: familiar icons, a tiny gallery of sprites, the same blocky tiles that had made him smile at midnight. Jiro clicked Play — the routine he'd practiced for months — and the little window popped up, proud and square. It displayed the hero, the grass, the distant mountains. It was... not full.

If your Pixel Game Maker MV is not working, this article categorizes the issues by symptom and provides the technical solutions required to resolve them.