Fix "You can't make this change because the selection is locked", or you can't select text while using Word.
First, try restarting the computer. Sometimes this is all that is needed.
Quit Word. Make sure you are in the Finder (AKA Desktop). Click the "Go" menu, and choose "Library". Note: If you don't see Library, hold down the option key while doing this. Find the folder called "Containers" and open it. Find the folder called "Microsoft Word" and delete it (drag to Trash). Restart Word
Or, in Terminal: Quit Word Erase: ~/Library/Containers/Microsoft Word Restart Word
If this doesn't fix the issue, do a restart, and this should resolve it.
TIPS PAGE