You can download Box Shot 3D here: https://boxshot.com/downloads/
Scroll down to the bottom of the page and download either 2nd or 3rd version of the software, depending on the license key you have.
If your license key consists of 4 blocks of digits, you need the 2nd version. If it consists of 5 blocks, you need the 3rd version.
If your license key is much longer, like 5 lines of digits and letters, you probably have Boxshot license and you can download a proper version here: https://boxshot.com/downloads/old/
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