2019 A4 Wired Car Play worked, but now does not.

[HeadlessChicken]

In my 2019 A4, Apple Car Play worked fine, so did Android Auto (Android hardly used).

Then a few weeks ago, Car Play does not connect.  I removed all the stored phones and factory reset the "Audi Smartphone" bit in Settings.  Plugging in the iPhone (iOS 16) gives prompt on MMI screen to activate Car Play, so it sees it, but then does no more.  If you go to Connection Manager, it sees iPhone in the Smartphone option, but it's not ticked.  If you manually tick it, the tick appears then disappears.  I tried a different iPhone with iOS 18, and changed the cable, same problem.

I plugged the Android in (not been used for a year), that did the same thing, tick appears then disappears, and Android screen showed something like there had been an error, device did not meet security protocols.  Something like that.  I forced the tick again, then Android Auto worked fine.

But iPhone refuses to work - it won't stay ticked, it looks like a handshake fails.  Phone does not react in  anyway when connected.  

Bluetooth connection works fine for music/phone etc.

Anyone seen before?