Now the error has changed to this:
Unfortunately SARS cannot perform a tax calculation based on the data submitted in your return. Please make sure you have completed your return correctly and try again. If this problem persists your return may require manual assessment.
That message is linked to the outstanding tax directive.
You should still be able to file the return, you will however get a message saying that your assessment cannot be issued and that it will require manual intervention by SARS, and that SARS will contact you when they are done (I have no idea how long this might take).
So you can go ahead and file the return OR you need to ask your Employer to contact the administrator of the transferee fund (the fund where you transferred to) so that they can file / apply for the necessary tax directive from SARS. Once this is done the message should disappear and then you can file
As a matter of interest, when was the benefits transferred from the original retirement fund to the new retirement fund (did it perhaps happen after 28/02/2018) ?