We found this information on a past case in our DB--sent to customer to review:
XCAS4R to XCMVS successful. XCMVS to XCAS4R via TCP/IP fails with XCM7050 error while checking password
and CPF2204 User Profile &1 Not Found. While USERID and PASSWORD are supplied, transfer runs
under the USERID that started XCOM. This USERID has TOTAL authority and access.
The AS/400 typically has all USERIDs in UPPERCASE. Placing the USERID in UPPERCASE resolved
the security error.
Customer replied that they acted on our remarks and the transfer worked out.