Completed up to Listing 25.9 - Obtaining FlickrFetchr: Failed to fetch items

I’ve followed the tutorial, and basically the code I have is exactly what is presented up to Listing 25.9, where you input the Flickr API key (which I had generated) and then modified the FlickrFetchr to add fetchItems() and PhotoGalleryFragment to add new FlickrFetchr().fetchItems();

My log:

11545-11563/com.bignerdranch.android.photogallery E/FlickrFetchr: Failed to fetch items
javax.net.ssl.SSLHandshakeException: Chain validation failed
at com.android.org.conscrypt.ConscryptFileDescriptorSocket.startHandshake(ConscryptFileDescriptorSocket.java:229)
at com.android.okhttp.internal.io.RealConnection.connectTls(RealConnection.java:192)

The log is quite long, but I hope what I’ve included explains the issue. I have no idea what to do, as I’ve double checked my code against the tutorial, and everything is there.