I was able to do it on the PC version. Make sure you download any updates and then start a new amended return. Or even uninstall and reinstall completely. e-filing is supposed to be be available for 1040X next month, so you may want to just wait a bit longer so you don't have to print it out and mail it.
Not that the IRS will get to it anytime soon anyway since there is now a huge backlog... My return was sent in May and it still doesn't show in the IRS system.
