Thanks Josh, I made a typo as I was using test-slideshow, not underscore.
I did manage to get the code read on the page but the message back was “no images found” because I didn’t have any featured images set, due to the error messages I keep getting.
I thought that I was able to set a featured image by going back from the error message but that didn’t work when I tried to lead the slideshow to the page. There’s no featured image, just an attachment.
I’m having this same problem and I’ve followed the suggestions only I still can’t select the featured image, I keep on getting an error message and a “try again later”.
I just realized that the reason the slideshow is not coming up is because none of the photos uploaded correctly as set featured images.
Any suggestions on how to fix this problem with uploading images?