You are registered in the UK, but you are currently posting on the US ebay.com discussion boards.
What are you trying to do when you get that error?
Is the error from eBay directly, or from a network provider?
The only reference to a 402 error on eBay that I can find refers to an email address being too long.
https://developer.ebay.com/devzone/xml/docs/Reference/ebay/Errors/errormessages.htm
