@Gooooo1 the error puppy is not the same as an offending prompt or image. That is normally the monkey (not kidding its the images they use). Can you share your first frame image? It could be too dark where Firefly can't determine the starting image. Try clearing the seed number (left column text box), brighten the image a little and reupload both first and last frames.
I'm sorry about the issue. Could you share the error you're getting? The screenshot does not show the error code. Please also share the complete prompts so we can try and replicate the issue. We are here to help.