Try opening the Android Auto app. on your phone & check 'Driving Mode' is not selected to 'Do Not Disturb'. I had a similar problem where my Music app was not showing up & turn by turn voice navigation was muted.
After changing this setting AA now appears to work as it should. Sounds like you...
Were you on the beta update program for P. If so have you opted out? I had to opt out before I got this month's update. Didn't realise you had to do this.
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AA has been doing this during the beta stages. I have the problem where sometimes it works & sometimes just a black screen on Pie
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It only stays on the navbar for around 2 seconds then disappears. It is noticeable as it has a small animation. Don't know why it shouldn't show on yours. Have you tried rebooting the phone & trying again.
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As far as I know it only appears when auto rotate is disabled. Working fine here. It's a very small button maybe you're just not noticing it.
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At the moment YouTube doesn't work in PIP mode. It only works in YouTube Red. There are very few apps that can do this. GMaps being one of them
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