Check focus assist isn't enabled:
- Click on the date/time in the bottom right of the taskbar
- Focus Assist settings
- Ensure this is off, or if "Priority only" is selected, you can customize the apps that are able to show notifications - make sure Wavebox is in the allowed list
Check notifications are enabled for Wavebox:
- Open the control panel
- Search for "Notifications & action settings"
- Locate Wavebox and click on it
- Ensure it's turned on and "Show notification banners" & "Show notifications in notification centre" are both checked
If both of those are enabled, there are a couple of other things to try:
- Clear all notifications, by clicking on the date/time in the taskbar and selecting "clear all"
- Restart the computer.