Does the script run corrrectly if you open the file with FMP advanced instead of the run time? That will answer your question as to whether the runtime is the issue or not.
You can also open the script in the script editor (using fmp not the run time of course) and double click the Import Records script step to see if you have correctly set up the external data source reference.
I have mostly solved my problem. My primary problem with solved with the script step SET VARIABLE. That tied it all together for me. I still have a little clean up to make it perfect. This little app has taught me about LET and variables.