Artifacts build as part of a PR are only available temporarily and for a short time (as PRs are development builds).
The artifacts of the referred PR are not available any longer. Therefore you get the error message.
That might be true but as i said the error occours also using the latest pull request which is only five days old.
I played around with Paulchen-Panther's script a little bit more, processed each step manually and finally found the github artifacts url for the PullRequest 1477
They seem not to be expired. Unfortunatelly haven't managed to download the corresponding zip file yet, but for me investigating the problem has a nice the side effect of learning.