Thanks, try following this post → 2016 Mustang Sync3 1.0 updated to 3.0 and no Apple Carplay! - #10 by SaNdMaN to install the intermediate 2.2.17xxx build and check if Android Auto works.
Also, you may need to swap the hub of the model is 2016 or earlier → Media Hub, CarPlay Compatible - 2015-2020 Ford/Lincoln - SYNC 3 , but do not do that yet.