Hi @Debbie
There's no built-in two-way sync between Gmail and Teams, which is probably why nothing you've tried has stuck. The Teams calendar is really your Outlook (Exchange) calendar, and it only shows your main calendar. So the trick is getting your Gmail events into that main calendar. Pick whichever fits:
- Automatic sync with Power Automate (best option). Go to make.powerautomate.com, create a new automated flow with the Google Calendar trigger "When an event is added, updated or deleted", then add the Office 365 Outlook action "Create event" pointing at your default Calendar. New Gmail events then appear in Teams on their own.
- View only, via subscription. In Google Calendar, go to Settings > your calendar > Integrate calendar and copy the "Secret address in iCal format". In Outlook on the web, click Add calendar > Subscribe from web and paste it. Two catches: it only shows in Outlook, not in the Teams calendar, and Outlook only refreshes these every few hours. That slow refresh is usually why it "doesn't update".
- The other direction, if it helps. To see your Teams meetings in Gmail, in Outlook on the web go to Settings > Calendar > Shared calendars > Publish a calendar, copy the ICS link, and in Google Calendar add it under Other calendars > From URL.
If your Gmail is actually a Google Workspace work account, your IT admin can also turn on free/busy sharing between Google Workspace and Microsoft 365, which lets each side see availability.
If this helped, please click Accept Answer so others trying the same thing can find it.
Reference: https://support.microsoft.com/en-us/office/import-or-subscribe-to-a-calendar-in-outlook-com-or-outlook-on-the-web-cff1429c-5af6-41ec-a5b4-74f2c278e98c