Text is not updating as I type

Have you tried with a different font?  That probably won't make any difference but it is worth a shot.

Is your graphic card driver up to date?

And here is another long-shot.  In the Edit>Preferences>Performance dialog, is your graphics card detected?  And, if so, try changing the box that I have marked in the following sceenshot.

Your video is very helpful, but can you make another one showing your entire workflow from creating the text layer with the text tool. 

What happens if you simply click and start typing with the text tool instead of drawing out a placeholder for the text?

Also, does it make any difference if you change the text alignment to left/right-aligned?

What happens if you double-click on the existing text, click at the end of the selected text so that the highlighted text is unselected, and start typing again?

Try resetting the preferences file. Go to Edit>Preferences>General tab and click the Reset Preferences on next launch button.  If that doesn't work, please give us a detailed step-by-step example of what you doing and what is not working.  If possible show us screen captures of the problem.  (Better yet, would be a video capture.)