If you have the data in CSV format, then you are probably better off importing it directly, rather than converting to XML.

When you import, you should have the ability to preview the data.  Have you tried that?  This will give you a good indication of the data.

As for not seeing the data once it has been import, it is possible that there are access rights at play here.  If you have Team Management enabled or if you require user assignments, then imported data that does not match this criteria will be invisible.  If this is the case, then you will need to login as admin to resolve the issues.