There are a few hosting platforms that require a bit of additional setup. Below are the ones we know.
Byte – Hypernode
After a fresh install on the Byte/Hypernode platform, the Magento API is not directly accessible.
Please see the following KB article to read about how and why parts of the Magento API are not accessible by default.
Check the .htaccess file that comes with your initial setup, it might be that /rest/ is blocked. Just remove that line from the files and you should be good.