I had the exact same problem (needed at least 3h to figure it out). In my case I use Solidworks to make the models, then export them to STL files and import them to blender to export them to FBX. What worked for me in UE is to click on the object taht the material is not working, then go to - Modeling mode(Shift+5) / UVs / AutoUV (the only thing you need to change is probaby the Auo UV method, select the mode that is most suitable to your object shape) then click accept. Hope it helps.