I click on "Amend (change) 2018 return" and none at all happens. How can I make it work?

Close the window for the TurboTax online account.  Clear cache and cookies on your web browser.  Close your web browser.  Sign back onto your TurboTax account - https://myturbotax.intuit.com/

Scroll down to the bottom of the screen and on the section Your tax returns & documents click on Show.  Click on the 2018 and Click on Amend (change) return

What happens after you click on Amend (change) return?

The 2018 amendment program needs to be downloaded and installed ... see if the installation file is hiding under the open window.