3654913 - Error 11001 WSA HOST_NOT_FOUND - MFC DC

Error when trying to connect direct connect service via ISQL:

=====

TCPIP Network Error: { [NOTCONNECTED] Lost connection to database,,

Request(Connect),SubFunc(Failed), SYBTCP RetCode(1) Description(SYBTCP_FAIL),
TCP API RetCode (11001) Description(WSA HOST_NOT_FOUND) } <HostName=xxxx>,
<PortNumber=1111>, <Region Name=cics01>, <TPName=yyy>
Msg 30000, Level 16, State 0:
Server 'DDDDD':
Login failure. <SMR>
CT-LIBRARY error:
ct_connect(): protocol specific layer: external error: The attempt to connect to the server failed.

=====

In the log:

======

isql NETWORK ERROR: SYBTCP ERROR INFO:, Request(Connect),SubFunc(Failed), Request(Connect),SubFunc(Failed), SYBTCP RetCode(1) Description(SYBTCP_FAIL), TCP API RetCode (11001) Description(WSA HOST_NOT_FOUND) errmsg[Win NT system call sybtcp_connect: gethostbyname, error num 11001, tranaction YYYY, region name CICS01, host name XXXX, port num 1111 ]
isql Error: 30261 Severity: 10 TCPIP Network Error: { [NOTCONNECTED] Lost connection to database, , Request(Connect),SubFunc(Failed), SYBTCP RetCode(1) Description(SYBTCP_FAIL), TCP API RetCode (11001) Description(WSA HOST_NOT_FOUND) } <HostName=xxxx>, <PortNumber=1111>, <Region Name=cics01>, <TPName=yyyy>

======

Mainframe Connect DirectConnect (MFC DC) 15.0

MFC, Mainframe Connect, DC, DirectConnect, Direct Connect, WSA HOST_NOT_FOUND, 30000, 30261, SYBTCP_FAIL , KBA , BC-SYB-MFC , Mainframe Connect (MFC) , Problem