Video Doorbell not detecting people until they are leaving

Over and over my video doorbell doesn't record or alert me until the person is leaving the porch.  This happens with the mailman all the time. He comes all the way up the walkway, puts the mail in the mailbox which is right in front of the doorbell, then is walking away from the house before I get an alert or the video starts.  This happens frequently--not recording anything that is happening right on my front porch. Last night we came home around 9pm and unloaded packages to the front porch and it didn't register anything at all.  Does anyone know how I can fix this?  Connection tests always say full blue bars (and I run the immediately after this occurs).  Also the camera is set to the highest sensitivity. 

Overall this doorbell is a huge disappointment. I would return it if today wasn't the last day of the return window and I had another one to install!