Hello there @tudorelufails!
Yeah, I have encountered this one myself more than a few times, please make sure UE is picking up that the map being imported is normals. It could miss sometimes. and in those cases, you need to open your texture, check the details panel, and ensure that Compression Settings are set to “Normalmap”, and that sRGB is unchecked. Adjust both settings, apply, and save.
If the issue persists, it could be a bit more technical, like testing between DirectX/OpenGL formats, or playing around with the green channel. Please check the following short guide for those options:
Hope this helps, and good luck!