Firebird 4.0.0 was released on 1st June. A small change from Firebird 4 rc1 has exposed a typo in the Firebird Pascal Interface file FB30Statement.pas that can result in an unknown data type error.
This has been fixed in the SVN release, but has not yet been progressed into the release zips. There will be a few days delay before re-issuing the zip files. This delay is intended to ensure that no other bugs are reported that affect Firebird 4.0.0 users.
To update from SVN see https://mwasoftware.co.uk/svn-repository