Have you made the phones forget about Sync3 as well?.
If you haven’t done so, do that and try again.
If you:
- have replaced the hub for a compatible one (Media Hub, CarPlay Compatible - 2015-2020 Ford/Lincoln - SYNC 3)
- have performed a master reset
- have made the phones forget about sync3
- have tried both android auto and car play
Then there’s really not much to try.
You can’t go back to 2.2, that’s why it’s always recommended to make sure AA/CP works on 3.0 or below before going to 3.4.
Does this mean brands or you tried 2 iphones?.
I’m asking because Android Auto is more forgiving, you could actually get AA to work with older unsupported hubs… But not CP…