The first thing to do with any such problem is trying to find the reason. You are not helpless when your project does not work, but have many possibilities to find out what's wrong.

If a shader does not work, first check the shader in the shader viewer. Then you'll see if the problem is related to your PC or your model.

If it's your model, check if the second skin is really not assigned to any triangle. If it is, the engine assumes that this skin is just another color texture and no normal map. Another possibility is that your normal map contains wrong content.

If the bumpmapping shaders don't work at all on your PC, check the video driver. Problems of this kind can be caused by installing a driver for a wrong card, or vice versa.