If you're having trouble with correcting the file, I'd suggest contacting our Phone Support Team. This way, they can further check on the file and help you correct it so you can get back to working order.
You might want to check out these articles to learn more about importing IIF file:
Once done, go back and try to export the employee list, then import via the IIF file. For more guidance, feel free to check out this article: Export, import, and edit IIF files.
If the issue persists, I highly recommend contacting our Phone Support Team. This way, they can investigate the issue further and provide additional troubleshooting steps to get you back to working order.