What's the support case number? What version of AirWave? Is AirWave collecting data over SNMP or AMON for your clients?
If AMON, make sure that you're running AMP 8.0.4.1 code for latest AMON fixes. Also, does AirWave have valid credentials for the controller to access telnet/ssh (needed for retrieval of missing client data). If not, then AirWave is unable to perform ExecUI queries to retrieve base xml state (catching existing clients), it will only reflect clients that have had a recent associate.
If SNMP, what's the output of:
# s2w <controller_ip> <community_string> nUserName -On
If using IPv6 -> nUser6Name
If the output looks accurate, try piping to line count:
# s2w <controller_ip> <community_string> nUserName -On | wc -l
The number of lines should match up to what AirWave is displaying for user count.