A family of Microsoft word processing software products for creating web, email, and print documents.
In what way does the feature not work? Do you receive error messages?
If Track Changes turns off unexpectedly, check if you could be pressing Ctrl+Shift+E by mistake (toggle command).
If you are saying that the changes do not display properly, then the selected settings will be relevant (as already suggested by Jade Ng).
Typically, you want to display "All Markup" and you want to verify the settings in the Advanced Track Changes Options dialog box. See the screen shot below.
To display the dialog box, go to the Review tab. In the Markup group, click the dialog launcher icon (the little arrow on the bottom right) and then click Advanced Options.