For next time though, the policy is you use send each order separately;

https://www.ebay.co.uk/sellercentre/postage/simple-delivery

If your buyer has purchased more than one item from you in a single transaction, you’ll receive one prepaid label for posting your items to them. You can only use the label provided once.

If your buyer has purchased items from you in different transactions, you’ll receive separate postage labels to post each of the items.