Http error: 406 – Not Acceptable
A 406 not acceptable status code is an error that occurs when a server is unable to provide the requested resource. This can be due to a number of reasons but usually indicates that the server does not have the requisite permissions to access the resource. In order to fix a 406 not acceptable error, you will need to ensure that your server has the correct permissions.
An example of a 406 not acceptable error would be if you were trying to access a website that was only available in certain countries. If your server was located in a country that was not on the list of allowed countries, you would receive a 406 not acceptable error.
The significance of a 406 not acceptable error to SEO is that it can prevent search engines from being able to access your website. This can lead to your website being ranked lower in search results, or even be removed from the index entirely.
RFC #: 7231 Section 6.5.6