The bread doesn’t rise and remains doughy—why?

 4 main reasons: ① Yeast touched salt/sugar directly and lost activity; ② Expired/poorly stored yeast (seal and refrigerate dry yeast); ③ Wrong ingredient ratio (too little water/too much flour, hard dough); ④ Too low room temperature (＜20℃, slow proofing—place a bowl of warm water next to the machine to raise the temperature).