Try, then, starting Windows in safe mode with networking.

I suspect there is another program hijacking your keyboard. I know I use at least two other programs that mess with my Word built-in shortcuts. Nei, thther does it to the Home key, though.

That the undo appears in the QAT tells me that likely you accidentally removed it. Remember that Ctrl+Z is undo, as well. You should be able to add it back by right-clicking on the QAT or Ribbon and selecting Customize the Quick Action Toolbar...

For what it is worth, I can confirm that Ctrl+Home and Ctrl+End act as expected in Word 2016 on my computer.