I recently came accross this “bug” with the Google Phone app and I thought it would be good to share the solution, since I couldn’t find it anywhere and I had to discover it by myself. It happened on my girlfriend’s Xiaomi Mi A1 with Android Pie but there’s a chance she was the only person in the world affected by this. You tell me.
The main problem was the fact that, all of a sudden, she was unable to see if there was an ongoing call in the background when the phone was locked, except for the tiny little “Return to call” at the bottom of the screen. I still have no clue on how that happened, but I had to fix it.
When the phone was unlocked, the notification was still visible in the notification bar, but minimized.
I initially thought it had something to do with Google’s recent addition of “chat heads” for ongoing calls, but at the end it was just a notification’s behavior problem. And the solution was actually pretty simple.
To restore the lockscreen notification, just long press on the actual notification during a call (or if you can’t make a call right now, go into Settings > Applications > Phone > Notifications) and open the Ongoing calls category. Inside the Behavior menu, you’ll see that it’s set to “Show silently and minimize“, that’s it. That’s the problem.
All you have to do is change it to “Make sound” and everything will be fine. The priority will change back to the original state and you’ll finally see the ongoing call notifications on your lockscreen again.
Hope it worked for you. Remember that you can leave a comment below if you need help.