To confirm your M1 Extension is using the correct Agent token:
Agent Token
" field in the Magento Extension requires a Zendesk API token created within the Zendesk admin screen. This token should be 40 characters in length.
3) In the sidebar of that Zendesk window, select Admin(cog icon) > Channels > API. The Zendesk API page is displayed.
4) Under the "Token Access
" heading, you can view your current active tokens, or use the + button to add a new token.
API Token
" field in step 1.