A template without the @name or @match attribute is not allowed. Add at least one of these arguments, otherwise the template cannot be applied.
Incorrect:
<xsl:template>
<!--body-->
</xsl:template>
Correct:
<xsl:template match="o/o">
<!--body-->
</xsl:template>
or:
<xsl:template name="oo">
<!--body-->
</xsl:template>
or:
<xsl:template name="oo" match="o/o">
<!--body-->
</xsl:template>