Undo won't work MS Word 365 on Windows 10

Of course, if you haven't changed computers recently, that rules out a keyboard issue, at least if the problem is limited to Word/Office.

Note that almost any program can install an add-in without asking you first, and there are many poorly designed add-ins out there.

A quick way to test for poor coding is to see what happens when running Word in (application) Safe mode.

I think we can end this discussion.

Ctrl z was working very well up to the day I went to the New Office. Then it stopped working.

I think I will wait and see what happens over time. Some other behavior issues in 2016, e.g. sorting in a table if there was a vacant row have gone away, I hope several others will also. The confusion we have shared is due to the difficulty of accurately describing a situation within the program.

I have not installed any add-ins. 

regards, bye

Some how we are not communicating. I have Win 7 up to date. Office 2016. Ctrl z does nothing.

Open Normal.dotm,>Options>Customize Ribbon>customize Keyboard>catatgory all>editundo. 

For undo it lists ctrl z, which does not work, Alt z which I added and does work, and Alt Bksps which does work. What has happened?

In a previous post, you wrote, "I looked into Keyboard assignments. Undo is listed but crtl z  does not show." That is why I thought you couldn't find Ctrl+Z in the list of the assigned commands.

OK, since Ctrl+Z is there but not working, the problem could be with your computer's setup. Some keyboards require that you press the Fn (Function) for certain keys to work as expected. Often, the Fn key must be used with the F1–F12 keys, but it is worth testing it even with Ctrl+Z.

You could also have a look at the BIOS settings and see what, if anything, can be customized there.

If the above fails, have a second look at troubleshooting add-ins.

Some how we are not communicating. I have Win 7 up to date. Office 2016. Ctrl z does nothing.

Open Normal.dotm,>Options>Customize Ribbon>customize Keyboard>catatgory all>editundo. 

For undo it lists ctrl z, which does not work, Alt z which I added and does work, and Alt Bksps which does work. What has happened?

Since you are not allowed to (re-)assign the shortcut successfully, try opening the Normal template as a document, assign the shortcut, save and close the file.

The quickest way to open Normal is by using a quick macro "trick": From within Word, press Alt+F11; the Visual Basic Editor displays. Press Ctrl+G to activate the Immediate window. Type

NormalTemplate.OpenAsDocument

and press Enter. Normal opens in a separate window (and you should now close the Visual Basic Editor). Make the changes, as discussed above. Save and close when you are done.

The next step is to figure out what is preventing you from saving to Normal. You can troubleshoot poorly designed add-ins by following the manual steps in the article at https://support.microsoft.com/en-us/kb/921541.