I need to amend my 2016 Tax return, but TurboTax says that I've passed the deadline to do it online however I can do it with the desktop version. How do I continue?

I purchased the online services, but how do I get the Desktop version to get the amendment done?  I've clicked on the help link on the popup to "Amend a return", but it appears to be broken.

Thank you for your help!