The failed print requests page on the history tab only contains print requests that have failed, whereas the print requests tab displays all that have succeeded and failed. This tab makes it easier to see where there was an error.
Whenever you encounter a failed print request and you are not sure how to fix it, you should open the request's log and send it to skipjack. You will be able to see what the error is at the bottom of the log.
You can access the log by hovering over the print request, in which a few buttons will appear to the right side and you'll notice that there's a blue one that says 'log'. This 'Log Data' is what you should send to skipjack.
Once you have fixed the bug in the script, you are able to retry by scrolling over the request again and clicking the green 'retry' button. When you retry, you are also able to change your printer.