So if you are prompted to enter an activation code, then you have most likely purchased the managed version, which is for businesses and requires an annual licence.
Quote from the FAQ on the manufacturer's website:
When I run the software on my new D300 key, it requires a code activation. How do I get this code?
It appears that you have a D300 Managed (D300M) drive. IronKey Enterprise devices are designed for large scale deployment using the centrally managed IronKey Enterprise Management Service. A separate annual licence must be purchased for each device. This management service issues the code for activation and is managed by an administrator. A minimum of two devices must be purchased for an Enterprise account. This drive cannot be used as a secure USB standalone drive.
Please exchange the product for the Basic version if you use the product privately rather than in a company.
Enclosed is the Basic Version:
Kingston IronKey D300 Encrypted (4GB, USB 3.0, 256 bit, Waterproof)