cs193p "Could not build objective-C module Twitter"

Question

When I drag the Twitter.xcodeproj into the workspace alongside Smashtag.xcodeproj, the Twitter.frameworkis red-flagged.

When I add

import Twitter

the compiler throws an error saying

Could not build objective-C module "Twitter"

I've seen the suggestions on the previous thread, but

1. when I try to convert the Twitter.framework to Swift3 when it's open by itself, it says that it already is in Swift3,

or

2. if I go to Edit -> Convert -> To Current Swift Syntax while in the workspace, the only option I get is the Smashtag.app

I'm certain that both Twitter.framework and Smashtag.app are in Swift3, yet the compiler throws an error saying that it can't build.

Any ideas what is going on?