RTC Build agent on z/OS AUTH Unable to set user account to *AuthUnknownUser

Hi,

We have installed and configured Build System toolkit and Build agent on z/OS. we did the RACF customization and started the agent with STC using STCBFA.

We did tso netstat we see the port 5555 is listening.

When we tried to connect via RTC client
we are getting the below message.
Message: Socket created successfully.
AUTH Unable to set user account to *AuthUnknownUser ("IBMUSER")
Authentication Failed.

We tried to telnet to the system using agent port 5555
200 HELLO - BuildForge Agent v8.0.0.1-0-0016

username IBMUSER
password XXXXXXX
cmd ping
go
320 AUTH AuthFail[*AuthUnknownUser,"IBMUSER"]
                                             251 RESULT 1
                                                         260 EOR


Please let us know what are we missing.

Regards,
Sathya