My best guess is that the material in Unreal doesn’t have anything connected to the opacity, and/or the material itself is Opaque
Need to set it to masked, or transparent, then be sure to connect the alpha channel of that texture to the opacity of the material (or opacity mask)
The texture either doesn’t have an alpha channel, or the transparency isn’t connected in the material in Unreal Engine.
That could be an issue related to how it was exported, or how it was imported.