Hi,
it's strange that you did not have return code = 4 when transporting to a client of the same system before, because I always had this rc when testing ChaRM with 3 or 4 clients in the same system. This is not because of ChaRM, but it's how the import works. I never had rc = 0.. But please note that rc=4 is not an error, it's just a warning and as you are testing using the same system, you can just ignore.
Regarding the message "Details: No import into test system has taken place yet", I have faced this many times and I hate it. If you run a Recheck, does it delete the error and understand that the import finished? Sometimes it's because the import takes longer and the program finishes without getting the return of the import. If it's very common that the imports in your system takes long time, there is a parameter CHECK_NTIMES_SOCM that you can insert in the users profile that can change how long the system waits for the import to finish. This parameter by default is 5, which means that the system will wait for 5 x 5 seconds before it returns. If you increase this parameter, the delay will be longer ( 5 x the paramater) and it may stop the error message in case the reason was a very long import time. But the higher is the parameter number, the longer you will wait looking at the Web UI until it finishes... And you should not set this parameter to more than 20 according to SAP to avoid very bad performance or even a time-out dump.
It also happened to me that the cause of this message was a problem in SMSY. The domain controller of the systems was not saved in SMSY (you have this field there for every system) and the program was getting lost because it was looking for the systems in the track based on the domain controller found in SMSY and as nothing was found it was not connecting via RFC to the managed system to get the result of the import.
Regards,
Raquel