UV unwrapping maps in blender not working


My first Post. So first i want to thank and say I love this community. I have found more answers to my questions than i did learning JS.
I am new to unreal, and blender, and all of it, substance 3D, Zbrush all the things ive used lately.

My question is; I built a house in Blender. My first problem if it helps the question was although i followed a tuturial nearly exactly… every single face was inverted and showed invisible in unreal. I fixed this by manually flipping the faces, so thats a bonus question if anyone knows why. i then grouped/combined my objects for export as I had near 100 pieces i had to try put together.
As seen in the screenshots I have come to a new problem, my railings in particular are BLACK… from what I read, it might be my UV maps.
So ive tried to apply/unwrap UV maps for all parts of my house… I successfully unwrapped for other objects, like clothing for metahumans… but this house… does not give me a UV map. Is there something i am missing.
I have tried smart uv unwrap… normal unwrap… etc…
Id really like to know this, as I wish to create 10s more kinds of houses for my dream game. And it become a problem importing to substance3D too, which i tried to get past by not importing UV at all.

Can anyone help as to why/how to unwrap this house UV?

P.S. the house material is set to like an XRAY green… the Railings are set to the same material… but show black… indicating a light issue?

Much appreciation if anyone can help/direct as to why.

Getting UVs from Blender to UE should be straightforward.

Can you show the UVs of the railings in Blender and UE?

Or you can upload an FBX of the railings here…