"The specified file is not a valid spreadsheet or contains no data to import"

Here's the problem:

You try to create a custom SharePoint list using the Import Spreadsheet function and get an error, "The specified file is not a valid spreadsheet or contains no data to import"

The problem is that IE doesn't have access to your file system, and in this instance, it needs it. The solution is to add the SharePoint site to your Trusted Sites zone.

Go to Tools / Internet Options

Click on the Security Tab, hightlight Trusted Sites and click the Sites button.

Enter the URL of the SharePoint site and click the Add button.

Close and Save your settings. You can now impor the spread sheet.