If your lemon meringue pie is not setting properly, several factors could be contributing to this issue. If the lemon filling is not cooked sufficiently, it may not set properly. Make sure that you cook the filling according to the recipe instructions until it thickens and reaches the desired consistency. The filling should coat the back of a spoon and have a pudding-like texture. Also, use the right thickening agent and the correct amount. Our lemon meringue pie filling uses cornstarch as a thickening agent. If the meringue layer is not properly cooked or if it's weeping (releasing liquid), it can contribute to the pie not setting. Ensure that the meringue is whipped to stiff peaks and that it completely covers the hot filling, with no gaps along the edges. Bake the meringue until it is golden brown and set.