Complete error message: Auth token is invalid, need help? Auth token is hard expired, User needs to generate a new token for this application.
This is a very common error, meaning your authorization token expired and you need to restore the connection between eBay and Nembol:
Open the Channels Tab
Disconnect eBay from Nembol
and connect it again.
If the first method doesn’t work, it means you need to grant access to Nembol again if you want to restore the connection. To do it, do the following:
Disconnect your eBay account from Nembol
Access your eBay account
Go to your account settings
Click on sign in and security
Scroll down to third party app access
Revoke all the authorizations to Nembol
Connect eBay to Nembol again.