It is because you write versionEntries
to the console. It is an object. If you are using IE, it will display as object instead of data in console. You can try using Chrome and check the console output value, it will display data from the object.
You can also try to use the SharePoint List web service that exposes Lists.GetVersionCollection Method to return version information for an item in a SharePoint list.
Here is a code demo to retrieve a list item version, it works.
<script type="text/javascript" src="http://code.jquery.com/jquery-1.10.1.min.js"></script>
<script type="text/javascript" src="http://cdnjs.cloudflare.com/ajax/libs/jquery.SPServices/0.7.1a/jquery.SPServices-0.7.1a.min.js"></script>
<script type="text/javascript">
$(function(){
$().SPServices({
operation: "GetVersionCollection",
async: false,
strlistID: "Lists_1",
strlistItemID: 1,
strFieldName: "Title",
completefunc: function (xData, Status) {
console.log(xData);
$(xData.responseText).find("Version").each(function(i) {
console.log("Name: " + $(this).attr("Title") + " Modified: " + $(this).attr("Modified"));
});
}
});
});
</script>