Are you running Android 9 or 10? Have you tried wiping the cache partition on your device:
1. Turn off the device.
2. Press and hold the Volume Up key and the Bixby key, then press and hold the Power key.
3. When the Android logo displays, release all three keys.
4. An 'Installing system update' message will show for 30 - 60 seconds before the Android system recovery menu options appear.
5. Press the Volume down key several times to highlight wipe cache partition.
6. Press the Power key to select.
7. Press the Volume down key to highlight yes, them and press the Power key to select.
8. When the wipe cache partition is complete, Reboot system now is highlighted.
9. Press the Power key to restart the device.
Have you tested your device in safe mode to see if you still experience these symptoms? Are you using a third-party launcher?
I have tried safe mode, the One UI launcher, and Nova launcher and none of them work. I've tried toggling through scheduled and always show modes as well and nothing seems to bring the AOD back.
Can I please have your full model number, baseband version, and service provider?
Do you have a theme on your device or an AOD screen downloaded?