On my 'Selling' page there a a number of options on the left side of the page. Under 'All Selling' is 'Manage postage labels'.

From memory, that allows you to (re)print a lebel, but I think it only works for 24 hours after generation.

If you got a confirmation email when you generated the label, that should also give you a link to 'Manage postage labels.

I know it doesn't help in this instance, but I have my browser set to download labels. That way I can print them from the pdf, rather than through eBay.