Hello Coolen
welcome to the Microsoft community, I'll be happy to help you today;
I understand that you have banner notification but they are not displaying in the button right corner
Initially, turn on Show taskbar on all displays option in Settings. To do that,
Right click on the Taskbar and click on Taskbar Settings.
Scroll down to Multiple displays and enable the option.
If the option is already enabled, disable it and reboot the PC. Later you may enable the option.
For more information, you may refer the article on Set up dual monitors on Windows 10.
https://support.microsoft.com/en-us/windows/set-up-dual-monitors-on-windows-3d5c15dc-cc63-d850-aeb6-...Also, select a display to alter the notification settings. Press and hold a display, then drag to rearrange it.
Once when the display is arranged, you may click on Apply. Narrow down to put a check mark on Make this my main display. By doing this, you will receive the notifications on your task bar.
Hope it helps.
