Payout timeframes range from region to region; however, the payout date provided in your admin is the date the funds will be sent to your bank account, but necessarily the day the funds will be in your bank account. While most banks process these funds within 24 hours; there are some banks that can take additional time to process the funds. Delays can typically be caused by regional holidays, and/or the funds being sent close to non-business days (weekends).
In terms of missing payments, I would look into the orders directly to determine if the orders were paid via Shopify Payments, or if they were paid through a different payment provider such as Paypal. You can view this by opening the order and scrolling to the "Order Timeline." - If the funds were paid via Paypal, then you'd need to reach out to Paypal to locate the funds; however, if they were paid via Shopify Payments, then the order timeline should indicate a payout date.
There is also the possibility that the banking information provided to us was incorrect (if this is your first payout) - If that were the case, we'd need to wait for the funds to fail, and be sent back to us before we can try depositing the funds again. If a failed payout happens, we'll send you a notice to update your banking information.
If you're still having issues with your payouts please let me know as I can verify the store to get this reviewed.