They are pottery items so can certainly see why you can't combine them. You'll have to cancel 8 transactions with the buyer's agreement. Then relist and ask the buyer to buy them again but this time to pay for each one separately. They may have to pace their purchases so ebay cannot combine.
It's ironic because sellers have been complaining for weeks about ebay not allowing combined postage. They have obviously made it easier and your case is the downside of that.