You actually have to take the monitor apart to get to the auto sync buttons on these toppers. My luck is when you adjust the settings, you dont have to go back into the settings again. One trick you CAN try is to unplug the VGA and plug it in again. See if it auto corrects. If not, you'll have to open up the monitor case.
If I remember correctly, I think I saw on Happ or the manufacters website there was a remote control that came with these toppers. Not sure if they are out there still but you might want to google it.