This sounds a great deal like a macro-related problem. I’m still wondering if the Word docs in question are infected with malware.

Actually it's a laptop with an attached Dell keyboard. I didn't like the laptop keyboard for several reasons, so I added an external keyboard which I like alot.

A few minutes ago, I used the original laptop keyboard, and tried Ctrl+A but same problem. It didn't select all. Didn't save the file by Ctrl+S either. So it doesn't seem like a keyboard problem.

Anyway, can you please suggest another way of (Select all) instead of Ctrl+A

Thanks

There should be a menu item for that. It should also be possible to add an icon to the ribbon.
CTRL+Home (cursor to first position), CTRL+SHIFT+END (select from cursor to end) should also select all.

Thanks

I found (Select All) in the menu. It's at the right end of the Home tab menu.
It works, but I also tried the other method ( Ctrl+Home -> Ctrl+Shift+End) , and gave the same result

Many thanks