Payouts once you are on eBay's Managed Payments are not instantly available for you to withdraw from your bank.
When you receive that email from eBay that your buyer has paid, and you need to post that item, eBay then first take their fees from money received from a sale, and send the remainder to your nominated bank account. This takes 1 - 2 business working days.
Your bank then takes 1 - 4 business working days to process those funds, before they become available for you to withdraw.
Weekends also prolong the process a little being non working business days.
