[GTALUG] every time I log in to google or ebay from Fedora they think that it is the first time

When I log into google or ebay from my desktop, they think that I'm logging in for the first time from that device. For ebay.ca, it is painless: I get a warning message in email "if this wasn't you...". For google it is more annoying. It wants a second factor authenticator. This amount to a message on all my android devices, none of which are close by. I have to climb a flight of stairs! Any idea why these sites think my desktop is new to them each time? (I don't get this when I log in from an Android device.)