I don't have a shot of it right now, but it happened again when I tried to download an update for an HP printer driver from the App Store update screen. When I hit the update button, I get the request for my id and password on the screen of my iMac, but then it states that I need a six-digit validation number. Since I tether my computer through my iPhone to get internet service, a beep occurs on my phone, after I ask for the download, asking me to allow Apple to certify my location. I allow them to do so. Then I receive a six-digit validation code. But nowhere on my iMac screen do I have a box show up that allows me to enter the six-digit number. Is it the age of my computer (iMac purchased in Feb. of 2008), the version of the OS (10.10.5 - can't get the new one as I have insufficient RAM), or something else. Thanks for responding to my question.