This issue usually has to do with the configuration Google G Suite apps, specifically Google plus.
To address the issue please perform the following steps:
- Go to https://admin.google.com/ and log in using your admin account.
- Click Apps, then G Suite and finally Google+
- Click Edit service
- Under Service status, click ON for everyone and then Save.
- Changes may take up to 24 hours to propagate to all users. Please wait for a while and then try booking a new meeting to see if the changes made an effect.
Please Submit a support request if this did not resolve your issue.