Ricardo,
If you are getting the CLIENT USER ID value in the CLIENT-USERID in TIRSECV-CMCB, did you save that in the CLIENT-USERID of GLOBDATA and then try to pick that up in TIRCUSRX?
You do not say what value you get returned for TESTUSER in TIRCUSRX (for the EXEC CICS ASSIGN USERID API call) but that would be the userid the server application is executing under, regardless of what version of the TIRCUSRX exit you using. The userid the application is executing under should match the CLIENT-USERID .
Like Letha says, you may need to customize the TIRCUSRX to use the code for non-terminal transactions. You do not say what protocol you using but it probably is TCP/IP (listeners TISRVMSL or TISRVLIS) since you have Java clients and those are non-terminal server transactions.
And like Letha says, if after all this you still have the problem open a Support Case and we will work thru the details. And then we will post the resolution.
Regards,
Teresa