Issues with Peeking and Popping

I am building a contact app in Xcode 9, Swift 4, iOS 11 but I am having a tough time attempting to implement Peek and Pop into my application. Here's how it's supposed to work: The user is presented with their list of contacts on a UITableView. I want the user to be able to use 3D Touch to peek at a contact without having to open the contact and pop it if they wish to open the contact. I found a great tutorial at Techotopia on using 3D Touch but haven't been able to get it to work. Xcode is not giving me any errors, yet when I debug the app on my iPhone 8, it does not work. Here is my code:

func previewingContext(_ previewingContext: UIViewControllerPreviewing, viewControllerForLocation 
location: CGPoint) 
-> UIViewController? {
    guard let indexPath = tableView.indexPathForRow(at: location),
        let cell = tableView.cellForRow(at: indexPath) else {
            return nil }

    guard let detailViewController =
        storyboard?.instantiateViewController(
            withIdentifier: "InfoContactController") as?
        InfoContactController else { return nil }

    detailViewController.preferredContentSize =
        CGSize(width: 0.0, height: 600)

    previewingContext.sourceRect = cell.frame

    return detailViewController
}

func previewingContext(_ previewingContext: UIViewControllerPreviewing, commit viewControllerToCommit:
 UIViewController) {
    show(viewControllerToCommit, sender: self)
}

In the tutorial at Techotopia, they use this code in viewDidLoad to register the previewing delegate:

if traitCollection.forceTouchCapability == .available {
    registerForPreviewing(with: self, sourceView: view)
} else {
    print("3D Touch Not Available")
}

The above code prints "3D Touch Not Available" in my console although I was obviously using a 3D Touch capable device. So, I did some research on Google and found this code which works:

override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
    super.traitCollectionDidChange(previousTraitCollection)
    switch traitCollection.forceTouchCapability {
    case .available:
        print("Available")
    case .unavailable:
        print("Unavailable")
    case .unknown:
        print("Unknown")
    }
}

This is my code. It gives me no errors in Xcode but when I 3D Touch in the app, nothing happens and I do not know why.
Any help would be appreciated!


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