Beginning yesterday we began receiving the error:
[[Template core/admin/global/globalTemplate is throwing an error. This theme may be out of date. Run the support tool in the AdminCP to restore the default theme.]]

However when attempting to navigate to our AdminCP page we also receive the same error and cannot attempt to restore the default theme.  How do we get to AdminCP without a theme?

 

You would need to use recovery mode for this, so you can get in there. It could be a theme, or even a plugin/app

https://invisioncommunity.com/4guides/client-services/getting-support-r292/#recoverymode