Payments

I have sold an item and am waiting for payment .   Notification states the buyer has requested a total amount .  However, when I click on the icon to “send payment details”  I get a bold blue message  “invoices cannot be sent for items where eBay manages all or part of the postage. These items are excluded from this invoice “

 

tried the help section but just got a bot that doesn’t understand my question …..so don’t really know what to do next , any help appreciated