Unable to see gradient after adding to layer

Quick answer：

When you add a gradient to a layer and it doesn't appear, it could be due to several reasons. Ensure that the gradient is applied correctly, the layer is not set to 'hidden' or 'lock', and that the visibility of the layer is not turned off. If you're using a software like Photoshop, check if the gradient is visible in the Layers panel and that the blend mode and opacity are set appropriately.