Every time I've had an issue importing a step file, it was due to the the way it was exported.
Doesn't answer your exact question, but I am able to open STEP files in SW13-SP2, no problem.
Can you import other STEP files without a problem?
Can you post the problem STEP file?
I found the problem. It was with my default templates. When it tried to open a step file it could not find my default templates because of the default template file location in the system options. All is well now. Thanks for the help.