I noticed when I updated our WHMCS system this week that I can no longer run proper WHOIS searches on Ausrtalian TLDs (that is .com.au .asn.au .net.au and so on). It was showing whether the domain was available or not, but was no longer showing full WHOIS info. The fix is simple.

For WHMCS 7.0 and higher

Create a new file called whois.json and upload to your WHMCS folder /resources/domains/whois.json
Inside the file place the following lines:

[
{
"extensions": ".asn.au,.com.au,.edu.au,.org.au,.net.au,.id.au",
"uri": "socket://whois.ausregistry.net.au",
"available": "---Available"
}
]

For WHMCS versions prior to 7.0

In your WHMCS /includes folder add these lines to whoisservers.php:

.asn.au|whois.ausregistry.net.au|---Available
.com.au|whois.ausregistry.net.au|---Available
.edu.au|whois.ausregistry.net.au|---Available
.org.au|whois.ausregistry.net.au|---Available
.net.au|whois.ausregistry.net.au|---Available
.id.au|whois.ausregistry.net.au|---Available

What was the issue?

The problem is that WHMCS is using whois-check.ausregistry.net.au instead of whois.ausregistry.net.au which is just returning the status Available or Unavailable instead of full WHOIS details. Do keep in mind that using whois.ausregistry.net.au there is a limitation of 20 requests per hour.  I imagine this is why WHMCS opted for the former but personally I prefer the later.