If you posted 8 separate transactions with one Simple Delivery label, then only one will show as dispatched, and you will not be able to add tracking for the other items.
The notifications to post will soon stop, but payouts for the untracked items will be held for a minimum of 14 days.
Combining postage is possible but many buyers , and indeed some sellers, do not know the process. Buyers need to place all items first in their basket, then at eBay checkout eBay will combine postage.
Might be an idea if you wish to combine future items, to add something like this.... ' I'm happy to combine postage, but to make this possible, please first place items in your basket, then at eBay checkout, the postage will be combined, thank you.'
@vinylbc2