Check what on my end? The same files import with serious errors and missing materials in 5.5 and work fine in 5.4, and imports correctly when reimported into 3dsmax. The FBX file is verifiably correct. The problem is something with Unreal 5.5.
I have altered no settings, the engine is in its default configuration. I will look into whatever interchange is and see if it makes a difference, but the default importer should still be fixed.