Try to add following entries in your "onlinemapsources.xml".
<cacheable>1</cacheable>
<downloadable>1</downloadable>
<maxtilesday>0</maxtilesday>
<maxthreads>0</maxthreads>
Here is an example.
<onlinemapsource uid="1">
<name>Earth</name>
<url><![CDATA[http://khm{$s}.sample.com/kh/v=76&x={$x}&y={$y}&z={$z}]]></url>
<minzoom>0</minzoom>
<maxzoom>18</maxzoom>
<projection>MERCATORESFERICA</projection>
<servers>0,1,2,3</servers>
<httpparam name=""></httpparam>
<cacheable>1</cacheable>
<downloadable>1</downloadable>
<maxtilesday>0</maxtilesday>
<maxthreads>0</maxthreads>
<xop></xop>
<yop></yop>
<zop></zop>
<qop></qop>
</onlinemapsource>