404 on Live Server

Are the operating systems on both the development version and the live version the same? It's possible that you have a filename casing issue. CodeIgniter 3 requires the first letter of the controller name to be uppercase and, since Windows and Mac are not case-sensitive filesystems, you might not see it until it's running on a case-sensitive OS like Linux.

But more details about things would be helpful:
- OS of both platforms
- version of CodeIgniter you're using
- what exactly is happening. (blank screen, 500 error, etc)

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