Rebates are automatically distributed as early as 48 hours after the order has been placed and if the order has been shipped.
The Manychat flow first checks your account 48 hours after the order was placed. If the order was marked as Shipped in your Seller Central, a Reward Link will be triggered, then flow will automatically notify the customer with the link to claim their rebate.
You do not need to do anything since this is automated.
If the order has not been shipped yet, the flow will wait another 24 hours before trying again.