[daimon]

Basic structure for Skindefinition.xml would be:

    <opt>                                   needed to start the file
        <SkinName Name="SKINNAME">            gives the #NAME# for the skin
            </SkinName>                     ends the naming tag
            
        <Panelfile>                         includes numeric values for panels
            <Element ID="PANELNAME">          child element for panelfile-tag
                </Element>                  ends element-tag
            </Panelfile>                    ends panelfile-tag
            
        <Mapping ArtAssetID="PIC.TGA">        refers to a picture used for skin
            </Mapping>                      ends mapping-tag
    </opt>                                  ends the file

If you're missing even a single </Element> tag that should be there in the correct location the skin won't show up in Lotro.

The problem might be a much more simpler too, hard to say.