he developers of the Gatehouse app have pushed out some fixes. Users will need to manually update their applications through the appropriate app store. This update should resolve the problem with sending passes to visitors via email.
Apple store: https://apps.apple.com/us/app/gatehouse/id1241656233
If you'd like to find all of the documents and information related to the Gate House project, please see the project page: https://www.bvcsd.com/projects/gate-access-control-system