If you put 'auto relist' into 'Help & contact' top left of your Ebay page, you will see all the terms and conditions.
You can still automatically relist 'buy it now' items, but not all sellers can use it for auction items - this is the relevant bit and why your items did not automatically relist:
'Keep in mind that the automatic relist option is only available on listings created by new and occasional sellers. The option will not show for other sellers.'
"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)