It looks like this is an issue today - there are now other posts in the forum about this.
I am not sure contacting Ebay Customer Services will help.
Personally, I would pay to post the items and cancel the unused labels.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)