When importing, you'd want to make sure you're logged in as the company's admin. Also, let's ensure to do it in a single-user mode. Let's first make sure that your QuickBooks software is updated to the latest release version.
Go to the Help menu from the opened company file.
Select Update QuickBooks Desktop.
Click the Options tab and click Mark All.
Under the Update Now tab, check the Reset Update.
Once ready, click Get Updates.
Once completed, let's reboot your device to ensure that all components are updated. Now, let's open QuickBooks and set it to single-user mode.
I can help fix the error when importing IIF files so you can get back to working order.
Based on the error in your original post, the troubleshooting steps provided by my colleague IamjuViel above should fix the issue. The main possible reason for the error is that you aren't logged in as the company admin.
If you still get the same error after logging in as the company admin, I highly suggest contacting our Phone Support Team. This way, they can check on your QuickBooks file and help you import IIF successfully.
To reach them, please follow the steps below:
Open your QuickBooks Desktop.
Go to the Help menu, then select QuickBooks Desktop Help.
Select Contact Us.
Give a brief description of your issue, then select Let's talk, and then choose a way to connect.