I can’t create layer for target layer to paint textures, i don’t know what to. do please help me.
You’re trying to blend a float3 (RGB) and a float4 (RGBA) together, so the computer can’t calculate the 4th value because RGB has an invalid fourth value.
You’ll have to put your heightmap on a different channel. For Normal maps this information is usually stored on the blue channel. For your diffuse texture, I would use the alpha channel unless there is no alpha. In that case you can just remove the heightblend all together in the properties window.
If you are interested in creating materials for landscapes I highly recommend this tutorial from the official documentation: https://docs.unrealengine.com/en-US/Engine/Landscape/QuickStart/4/index.html