Hi,
Initially can you check the below Tcode WE20(Check that the System are active state),WE21,BD64,BD54,BD97 and check the below mentioned table RSBASIDOC RSBKDTP, RSTRAN, TADIR, RSPCVARIANT, RSSTATMAN,... are not converted and pointing to the old system name.
Once all the above steps are green . We need to check the RFC and the user used in the rfc have proper access in both the source and the target system.
Hope that you would have already run BDLS to convert the entry of Production system for all the system conncted to BW and would have got the new id in BW system in RSA1.
Please let me know your input and see how we go from there.