Hi Phil,
Thanks for your update.
I understand major users in your organization encountered a new issue during accessing team site. As many users are used to accessing team site by clicking the Team Site bottom on the header of Portal page, and the link won’t continue to take effect after user changed the team site default URL. Would you like to perform the following steps to change the default URL back and see if any updates?
1. Access your team site Site Settings page by opening this URL: http://yourdomain.com/teamsite/_layouts/settings.aspx
2. Click Title, description, and icon under Look and Feel section->change web site address, type “teamsite” in the dialog box->OK, for example:
In addition, if you even cannot access your team site Site Settings page, I suggest you check the service status on Service Health page.
Admin page-> Click Service Health under Support->Check if there are any abnormal status in the form.
Thanks,
Maggie Li