The Gmail integration is there to provide a smoother emailing experience for you as a user.
The Gmail integration can be enabled under Settings > Integrations.
When you get an error while trying to integrate Gmail, you can try the following:
Disable the Gmail integration (from Settings > Integrations)
Clear cookies for HeroHunt.ai
Refresh the page
Enable Gmail integration again
Refresh the page once more and try to send again
If this doesn't work, please reach out to support or use HeroHunt.ai without integrating Gmail. You will still get the automatically generated messages that pop up after clicking on the 'Send' button.