If you get the error “Can’t send – User account cannot share structures’ there are two possible reasons.
has a G Suite Account
Google Assistant is not supported on G Suite accounts yet. If you try to add a G Suite users to Google Home, you will get the “Cannot share structures” error.
G Suite is the old Google Apps account. If the users email address ends with something other than @gmail.com, they are most likely using G Suites.
If this is the case, unfortunately there isn’t anything that you can do at this point. Wait till Google enables Google Assistant for G Suite account and try again.
Advanced Protection Program
For regular Google accounts if you are getting this error, check if the user you are trying to add is part of Google’s Advanced Protection Program.
Advanced Protection Program is a Google security solution for personal accounts. This offers additional security features to sensitive user accounts. For example, if you are a journalist covering controversial topics, you are most likely a regular target of security threads from various agencies around the world.
Advanced Protection Program offers a set of additional security features to safe guard your account.
Unfortunately, Google Assistant seems to be experiencing issues with these security layers.