I cannot get my messages app to notify me via sound or vibration when I get new messages. Checked the settings and I have vibration set to on and have selected and saved a sound. Even tried toggling these settings on and off but it didn't help.
I love my Pixel 4, and not getting any text message sounds would drive me up the wall. Let's make sure you get the alerts like you are supposed to. How are your other alerts on your device working (Email, phone calls, etc.)? Were there any recent software updates or changes to the device? Also, please be sure to do a soft reset (shown here - http://spr.ly/66041tUR4) on the device and see what changes in behavior come out of it. You'd be surprised how often this small action can fix bugs in devices. Keep us posted on your success!