Hi @RiCZrd.

The comment will appear on several of your mods because the game logs have errors related to them. I assume the situation is the same in each case.

There are multiple entries in the logs with your mod IDs, but they all refer to the same files ("blankspecular.dds" and "blankbump.dds"). They look something like this:
"C3DHelp_ReadFileIntoBuffer FAILED fopen(\steamapps\workshop\content\784150\MODID\blankspecular.dds)"
"C3DHelp_ReadFileIntoBuffer FAILED fopen(\steamapps\workshop\content\784150\MODID\blankbump.dds)"

From what I see, in "*.mlt" files you use "$TEXTURE_MTL", which means that the given texture should be in the same directory as the MLT file. If, as I think, you want to use the texture from the game directory, use "$TEXTURE" and the appropriate path. For example, in "panelak_moderny.mtl" there are these entries (they should work for you):
"$TEXTURE 1 buildings/blankspecular.dds"
"$TEXTURE 2 buildings/blankbump.dds"

Can you verify this?

Tolle Skins. Im Winter sehen die roten Dächer nicht so gut aus. Kannst du das Rot etwas dunkler machen, vielleicht mehr ins Ziegelrot gehen?