iOS, Android? Make sure notifications are turned on for that app via the notifications setting. If those look fine, on Android, delete app data and cache, force stop, then reopen. If that still doesn’t do it, uninstall and reinstall.

If you have root, make sure everything is gone from the data partition before you reinstall.

iOS, uninstall, reinstall.

This is all under the assumption that you have already tried the obvious, making sure the notification settings are turned on within primal itself.