That’s probably because you denied access to your keychain.
It might be required to renew the eBay token completely:
Remove your eBay account from the GarageSale preferences > Accounts, restart your Mac and then re-add your eBay account.
If this won’t help, please give this a try:
- Quit GarageSale if running.
- Open the macOS “Keychain Access” application and enter “GarageSale eBay Account” in the search field. (If you don’t find anything try it with “ebay token”.)
- Right-click on the eBay account token in the Keychain and select “Delete”.
- If done, restart your Mac, start GarageSale and add/refresh your eBay access tokens in the GarageSale preferences > Accounts.