Operator Panels are only as reliable as the client’s network setup.  MES is trying to determine if the connected PC is associated with an Operator Panel.  IIS only sees IP addresses. Therefore,  MES needs to request the Hostname of an IP Address from your DNS server, but your DNS server may not be able to properly resolve it to the correct Hostname.  MES relies upon the TCP/IP command “NSLOOKUP” to determine the HOSTNAME from an IP.  Therefore, if you enter “NSLOOKUP (IP4 of workcenter)” in a command prompt, does it return the correct hostname on your network?  If not, you’ll need to look into that networking/DNS issue.  Alternatively, that is why we recommend configuring operator panels by static IP address rather than hostname.