I generated a TeamGantt ICS calendar feed using Menu → Calendar Feed. The feed successfully subscribes and displays all tasks in Microsoft Outlook, but Google Calendar returns “Authorization failed” when it is added through Other calendars → From URL.

I tested the same feed in both a Google Workspace account and a personal Gmail account, and both failed. This rules out our Workspace administration settings.

Could you verify whether prod.teamgantt.com/gantt/export/ics/ics.php is allowing requests from Google’s calendar subscription service, including the Google-Calendar-Importer user agent, and whether the endpoint returns any redirects, challenges, cookies, or different headers to Google’s servers?