The Error

This error means that your eBay authentication token is in valid or cannot validate.

Causes and Solutions

1. Your authentication token has expired, this is generally caused by either change in account details (password, business name, address, etc), the other is a time expire, eBay do this for security reasons.

The solution to fixing this issue is to go to Settings -> Channel Integration > click Config next to the eBay account

• Click Test
• The system will prompt you that it cannot authenticate the account,
• Answer yes to Resubscription
• Go through the authorization form again

This will renew your authentication token. 

2. eBay's authentication service is not responding/unavailable.

• If this is the case then you will need to contact eBay to rectify the issue.