" The upgrade procedure went well,.....but I have multiple issues with the task bar area....no start menu, no Cortana or search,....."
After you upgrade to windows 10 again, check your computer for the latest windows updates,OS Build and Version in settings....
1. Click Start"s button at the left bottom of the taskbar, Settings, Update And Security, and then Check For Updates.
2. Check OS Build (10586.218) and Version(1511) - click Settings, System and then About
If the Start Menu doesn't work then right click the Start's button or press windows key and X key at the same time.....
1. Click Control Panel
2. Look under System And Security, click Find And Fix Problems
3. On the left, click View All
4. First, click windows updates, and then use the other troubleshooting fixes