Hello everyone.
The problem is that one of the meshes (in Blender it is “group_1”) does not appear when imported into Roblox Studio (it is simply invisible). And I don’t know what the reason for this is, if only because I’m not really experienced at it. And even after several days of research I couldn’t find anything, because the problem seems to be more complicated. And while I’m at it, is there a way to export the texture so that I can easily create a UV map with the colors from the meshes (in Blender), so that it is automatically applied or I don’t need a UV map at all?