Ring 3 Not Detecting a Delivery

I just had a delivery today from Amazon and the Ring 3 never saw it, despite the package being left right in front of it. Looking at the video, it shows no package then suddently the package is there as if it appeared out of thin air but the doorbell never recorded the person actually leaving the package and of course there was no notification. This has happened on a few occasions in the month that I've had this doorbell. Why does this happen and how can I fix it?