Did you try the solution the error message recommends?
5 – Start iSeries NetServer with the reset option using the Start
(QZLSSTRS) API. If the problem continues, restart TCP/IP with the
TCP/IP (ENDTCP) and Start TCP/IP (STRTCP) commands. Note: This may
other users. If the return code is 3420, see the recovery for
Searching the internet I found someone with a similar issue and this was the suggestion they were given:
Hope this helps you out:
After upgrading from V4R5 to V5R1, NetServer failed to start with
error CPIB683 reason code 5 return code 3420 in the QSYSOPR message
queue. Error 3420 indicates there is a name conflict on the network.
The NetServer name was configured to be the same as the iSeries system
name which should work. In testing, the name was changed to another
name and NetServer started successfully.
A Server Message Block (SMB) licensed internal code trace was taken.
The trace showed TCP/IP addresses of several PCs on the network that
had a group name conflicting with the NetServer name. To test this the
following command was run from a DOS prompt using the IP address of
one of the PCs identified in the trace:
nbtstat -a nnn.nnn.nnn.nnn *** substituting the PC IP address
The NetBIOS Remote Machine Name Table displayed showed a group name
matching the NetServer name. Checking the PC configuration verified
the Windows Workgroup name was the same as the NetServer. This is not
allowed by the NetBIOS over TCP/IP specification. In V5R1M0, this
portion of the code was rewritten to follow the NetBIOS over TCP/IP
specification more closely, and this is the reason the problem was
exposed with the upgrade to V5R1. The changes were intentional and
this is working as designed, in accordance with the specification. To
resolve the problem, the Windows Workgroup name on the PCs was