Looks like there are some missing items in the top and bottom of your file. Make sure you have the following surrounding your NAD clients.
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<TipsContents xmlns="http://www.avendasys.com/tipsapiDefs/1.0">
<TipsHeader exportTime="Fri Mar 10 12:23:40 EST 2017" version="6.5"/>
<NadClients>
<NadClient description="Unknown " name="172.19.0.38" coaPort="3799" coaCapable="true" vendorName="Unknown" tacacsSecret="" radiusSecret="" ipAddress="172.19.0.38"/>
</NadClients>
</TipsContents>